IGCSE G10 Mocks P1 - P5

Characteristics of optical image in a plane mirror

1. Same size as object 2. Same distance from mirror as object 3. Virtual image 4. Laterally inverted 5. Upright

Conditions for equilibrium

1. The sum of forces in one direction equals the sum of the forces in the opposite direction. 2. The law of moments must apply.

Fire risks

1. Use plugs with correct fuse. 2. Do not overload appliances to a circuit. 3. Don't overload circuits by using too much adapters. 4. Appliances such as heaters use large amounts of power (and hence current), so do not connect them to a lighting circuit designed for low current use.

Lever

A device which can turn about a pivot. In a lever a force called the effort is used to overcome a resisting force called the load, and to do work.

Shadows

Are formed for two reasons. First, because some objects, which are said to be opaque, do not allow light to pass through them. Secondly, light travels in straight lines. A small source of light, called a point source, gives a sharp shadow which is equally dark all over. A large source of light, called an extended source, creates much larger area of shadow with different darkness. The darker centre part is called umbra, where the outer lighter part is called penumbra.

P7

Atomic and Nuclear Physics

Concave lenses (e.g. peep holes on doors)

Concave lenses always produce images that are: Upright Diminished Virtual From the same side of the principal axis meaning the image will be upright Further from the principal axis, so the image will be larger than the object

Resistor

Conductors intended to have resistance, and are made either from wires of special alloys or from carbon. Those used in radio and television sets have values from a few ohms up to millions of ohms. Resistors in series = R1 + R2 + R3 Resistors in parallel = 1/R1 + 1/R2 + 1/R3

Simple a.c. generator (alternator)

Consists of a rectangular coil between the poles of a C-shaped magnet. The ends of the coils are joined to two slip rings on the axle and against which carbon brushes press. During the first quarter rotation the p.d. increases to a maximum when the coil is horizontal. The sides are then cutting the lines at the greatest rate. In the second quarter rotation the p.d. decreases again and is zero when the coil vertical. After that, the direction of the p.d. reverses.

Electric current

Consists of moving electric charges. Effects of a current: a) Heating and lighting (e.g. lamp) b) Magnetic (e.g. plotting compass is deflected when placed near the wire because a magnetic field is produced around any wire carrying a current. c) Chemical (e.g. bubbles of gas are given off at the wires in the acid because of the chemical action of the current.

Thermocouple thermometer

Consists of two wires of two different materials, such as copper and iron, jointed together. When one junction is at a higher temperature than the other, an electric current flows and produces a reading on a sensitive meter which depends on the temperature difference.

Uniform velocity

Constant speed in the same direction.

Projectors

Contain convex lenses. For an object placed between one and two focal lengths from the lens, the image is: Inverted Magnified Real In a film or data projector, the image is formed on a screen. Therefore, the film must be loaded into the projector upside down so the projected image is the right way up and enlarged.

Wind energy

Energy generated from the kinetic energy from blades of wind turbines. However, wind turbines can be noisy, and may be considered unsightly.

Electric power

Energy transfers are measured by the work done and power was define by the equation... Power (J) = Work done (J) / Time taken P = E/T Power = Current x Voltage P = IV

P2

Energy, Work, and Power

Battery

How a battery works: Transforms chemical energy => electrical energy. Because of the chemical action going on inside it, it builds up a surplus of electrons at one of its terminals (the negative) and creates a shortage at the other (the positive). It is then able to maintain a flow of electrons, i.e. an electric current, in any circuit connected across its terminals for as long as the chemical action lasts. The battery is said to have a potential different (p.d. for short) at its terminals. Potential difference is measured in volts (V) and the term voltage is sometimes used instead of p.d.

Resistance (R)

How hard it is for the current to flow through a circuit. Or the opposition of a conductor to current. A good conductor has a low resistance and a poor conductor has a high resistance. The resistance of a wire of a certain material... Increases as its length increases Increases as its cross-sectional area decreases Depends on the material, silver is the best, and copper is the next best, which is cheaper. Measured in ohms. The ohm is the resistance of a conductor in which the current is 1 ampere when a voltage of 1 volt is applied across it. R = V / I

Power stations

In the power station alternators, the electromagnets rotate while the coils and their iron core are at rest, the opposite to motors. The large p.d.s and currents (e.g. 25 kV at several thousand amps) induced in the stator (induction coils) are led away through stationary cables, otherwise they would quickly destroy the slip rings by sparking. Instead the relatively small d.c. required by the rotor (electromagnet) is fed via the slip rings from a small dynamo (the exciter) which is driven by the same turbine as the rotor. It provides electricity to the electromagnet to allow it to work.

Condensation

Gas changes to liquid state and a latent heat of vaporisation is released.

Speaker

Has a cone which is made to vibrate in and out by an electric current. The wave progresses through the air but the air as a whole does not move. The rapid pressure changes on the eardrum allows people to experience the sensation of the sound. # of compression per second = frequency of the sound wave,

Step-up transformer

Has more turns on the secondary coil than the primary and Vs is greater than Vp.

Crystals

Have hard, flat sides and straight edges. Whatever their size, crystals of the same substance have the same shape. This can be observed using a microscope. A trimming knife is used to cut crystals, by holding exactly parallel to one side of the crystal, and struck by a hammer.

Latent heat of vaporization

Heat energy given for change of state from liquid to gas or vice-versa.

Latent heat of fusion

Heat energy given for change of state from solid to liquid or vice-versa.

Displacement-distance graph

Helps explaining and describing waves, it shows, at a certain instant of time, the distance moved (sideways from their undisturbed positions) by the parts of the medium vibrating at different distance from the cause of the way.

Law of magnetic poles

If the N pole of a magnet is brought near the N pole of another magnet, repulsion occurs. Two S (south-seeking) poles also repel. By contrast, N and S poles always attract. The law of magnetic poles summarises these facts and states: Like poles repel, unlike poles attract. The force between magnetic poles decreases as their separation increases.

Boyle's Law

If the volume of a fixed mass of gas is halved by halving the volume of the container, the number of molecules per cm3 (pressure) will be doubled.

Parallelogram law

If two forces acting at a point are represented in size and direction by the sides of a parallelogram drawn from the point, there resultant is represented in size and direction by the diagonal of the parallelogram drawn from the point.

Refraction by a prism

In a triangular glass prism, the bending of a ray due to refraction at the first surface is added to the bending of the ray at the second surface' overall change in direction of the ray is called the deviation. For example, white light shining through cut crystal can produce several spectra

Electromotive force (e.m.f)

In energy terms, the e.m.f. is defined as the number of joules of chemical energy transferred to electrical energy and heat when one coulomb of charge passes through the battery (or cell).

Variation of resistance with temperature

In general, increase in temperature increases resistance of metals. But decreases the resistance of semiconductors when the temperature increases.

Toppling

Leaning over as if to fall. The position of centre of mass of a body determines whether or not it topples over easily. A body topples when the vertical line through its centre of mass falls outside its base. To increase stability of a body: Lower its centre of mass (height). Increase the area of its base.

Declination

measures the direction of magnetic north pole with respect to the geographic north pole. How off the magnetic north is from the actual geographic north pole.

Greenhouse

Light and short-wavelength infrared from the Sun penetrate the glass of a greenhouse and are absorbed by the soil, plants, etc., raising their temperature. These in turn emit infrared but, because of their relatively low temperature, this has a long wavelength and is not transmitted by the glass. The greenhouse thus acts as a 'heat-trap' and its temperature rises. CO2 and other gases such as methane act in a similar way, causing global warming if excess in amount.

Total reflecting prisms

The defects of mirrors are overcome if 45 degree right - angled glass prisms are used. Just remember when light enters this kind of prism, it turns 90 degree every time it hits a side inside the prism.

Wave equation

The faster something vibrates, the shorter the wavelength, and the higher the frequency will be. Speed of wave = frequency x wavelength

Current (I)

The flow of electrical charge between two points. The unit of current is the ampere (A) which is defined using the magnetic effect. One milliampere (mA) is one-thousandth of an ampere. Current is measured by an ammeter in a series circuit. Measured in Amperes. One coulomb is the charge passing any point in a circuit when a steady current of 1 ampere flows for 1 second which is... 1C = 1A s Current = Voltage / Resistance I = V / R

Conduction

The flow of thermal energy (heat) through matter from places of higher temperature to places of lower temperature without movement of the matter as a whole. At hot end, particles have more energy and vibrate faster, colliding with neighbouring particles to transfer energy / vibrations. Good conductors: Copper, aluminium, brass, then iron (in order of best conductors to good conductors). Bad conductors: Plastic, wood, and water.

Tidal and hydroelectric energy

The flow of water from a higher to a lower level from behind a tidal barrage (barrier) or the dam of a hydroelectric scheme is used to drive a water turbine (water wheel) connected to a generator. Problems : Large scale, can impact environment, may have floods, costly.

Pressure (P)

The force (or thrust) acting on unit area. Measured in Pascal (Pa) 1 Pascal = 1 newton per square meter Pressure = force (newton) / area (cm^2, m^2...etc)

Wave energy

The rise and fall of sea waves has to be transferred by some kind of wave-energy converter into the rotary motion required to drive a generator. However, this takes up large amount of space and can impact wild life / habitats.

Powers of lens

The shorter the focal length of a lens, the stronger it is, i.e. the more it converges or diverges a beam of light. Power of a lens = 1 / focal length of the lens (meters) P = 1 / f

Magnetic field

The space surrounding a magnet where it produces a magnetic force. The magnetic force is shown by a curved path AKA a line of force or a field line. The force between two magnets is a result of the interaction of their magnetic field.

Microwaves

Used for international telecommunications and television relay via geostationary satellites and also mobile phone networks. Also used for radar detection in the army. It is also used for cooking as it causes water molecules in the moisture of the food to vibrate vigorously at the frequency of the microwaves.

Motion sensors

Uses ultrasonic echo technique to determine the distance of an object from the sensor.

Unusual expansion of water

Water expands when being heated up and contracts when being cooled down. However, it expands between 4 - 0 degree Celsius. At 0 degree Celsius, every 100 cm3 of water becomes 109 cm3 of ice. It is caused by the breaking up of the groups that water molecules form above 4 degree Celsius. The new arrangement requires a larger volume and more than cancels out the contraction due to the fall in temperature. Water has a MAXIMUM DENSITY at 4 degree Celsius. Ice is less dense than cold water so it floats.

P4

Waves

Non-uniform speed

When a body travels unequal distances in equal intervals of time.

Floating and sinking

An object sinks in a liquid of lower density than its own; otherwise it floats, partly or wholly submerged.

Law of reflection

Angle of incidence = angle of reflection

P6

Electromagnetism and Energy Resources

Ray diagrams

1. A ray parallel to the principal axis is refracted through the principal focus, F. 2. A ray through the optical centre, C, which is undeviated for a thin lens. 3. A ray through the principal focus, F, which is refracted parallel to the principal axis,

Properties of the image in a plane mirror

1. As far behind the mirror as the object is in front, with the line joining the object and image being perpendicular to the mirror. 2. The same size as the object. 3. Virtual. 4. Laterally inverted.

Neutral equlibrium

A body is in neutral equilibrium if it stays in its new position when displaced, e.g. a ball.

Stable equilibrium

A body is in stable equilibrium if when slightly displaced and then released it returns to its previous position.

Unstable equilibrium

A body is in unstable equilibrium if it moves further away from its previous position when slightly displaced or released.

Parallel circuit

A circuit that contains more than one path for current flow. The current splits. Voltage total = V1 = V2 = V3 The sum of the currents in the branches of a parallel circuit equals the current entering or leaving the parallel section. 1/Resistance total = 1/R1 + 1/R2 + 1/R3 The voltages across devices in parallel circuit are equal.

Series circuit

A circuit which the components are arranged in a chain. The different components / parts follow one after the other and there is only one path for the current to follow. Voltage total = V1 + V2 + V3 Current is the same at all points in the series circuit Resistance total = R1 + R2 + R3 The voltage at the terminals of a battery equals the sum of the voltages across the devices in the external circuit from one battery terminal to the other.

Ohmic conductor

A conductor that obeys Ohm's law

Tickertape timer

A device enables us to measure speeds and hence accelerations.

Semiconductor diode

A device that uses a p-n junction to allow current flow in only one direction. It is a non-ohmic conductor. A diode (such as LED) has a small resistance when connected one way round but a very large resistance when the p.d. is reversed. That is why LED is a good device to prevent back flows in a system such as a solar panel and battery charging from it.

Progressive wave (Chapter. 25)

A disturbance which carries energy from one place without transferring matter. They are transverse and longitudinal waves.

Force

A force is a push or a pull. Has both magnitude (size) and direction.

Gravity

A force of attraction between objects that is due to their masses.

Centripetal force

A force that acts towards the centre and keeps a body moving in a circular path. Force = (mass of the object x velocity^2) / radius F = (mv^2)/r E.g. satellite orbiting. Orbital period = distance / velocity T = (2πr) / Δv

Friction

A force that opposes motion between two surfaces that are in contact.

Converging lenses

A lens that is thickest in the centre and bends light inwards. A converging lens forms a magnified image of a close object. Converging lens gives an enlarged, upright virtual image of an object placed between the lens and its principal focus. It acts as a magnifying glass. Converging lense table (practical) If object is placed beyond 2F... Image will be real and between 2F & F and is smaller and inverted. If object is placed at 2F The image will be real and at 2F, same size and inverted. If the object is between 2F & F... The image will be beyond 2F with a larger size and inverted. If object is placed at F... The image will be real and at 2F with the same size and inverted. This part is really confusing...

Diverging lenses

A lens that is thinnest in the centre and spreads light out. A diverging lens forms a diminished (smaller) image.

Wave front

A line on which the disturbance has the same phase at all points; the crests of waves in a ripple tank can be thought as wavefronts.

Solidification

A liquid changes to a solid and latent heat of fusion is given out. Energy is released into the environment when solidification occurs.

Long sight (Pg. 132)

A long-sighted person sees distant objects clearly but close objects appear blurred. The image of a near object is focused behind the retina, because it is either the eyeball is too short or because the eye lens cannot be made thick enough (opposite of short sight). The problem is that the angle of incidence enters from an angle that is too large. A converging spectacle lens corrects the problem.

Sound waves

A longitudinal wave consisting of compressions and rarefactions, which travels through a medium. Speed of sound: Air 0 degree celsius - 330 m/s Water - 1,400 m/s Concrete - 5,000 m/s Steel - 6,000 m/s

Magniflying glass

A magnifying glass is a convex lens used to make an object appear much larger than it actually is. This works when the object is placed at a distance less than the focal length. The image is: Upright Magnified Virtual Only the person using the magnifying glass can see the image. The image cannot be projected onto a screen because it is a virtual image.

Refractive index

A measure of how greatly a substance slows the velocity of light and the angle of rays. Refractive index (n) = speed of light in air or vacuum / speed of light in a medium Refractive index (n) = sin angle of incidence / sin angle of angle of reflection n = sin i / sin r

Filament lamp

A non-ohmic conductor at high temperatures. Its resistance increases as current increases and makes the filament hotter. A non-ohmic conductor at high temperatures. Transfers only 10% of the electrical energy supplied to light; the other 90% becomes heat and may last 1,000 hours.

Vector quantity

A physical measurement that contains both magnitude and directional information. Vectors : Velocity, displacement & acceleration

Scalar quantity

A quantity that can be described by magnitude only and has no direction. Scalars: Speed & distance

Variable resistor

A resistor whose resistance can be changed. Also called a potentiometer. Consists 60% of copper, and 40% of nickel.

Loudness

A sensory characteristic of sound produced by the amplitude (intensity) of the sound wave. How noisy or quiet a sound is. Louder sound = larger amplitude Quieter sound = smaller amplitude

Ripple tank

A shallow tank of water in which water waves are created by a vibrating dipper to study waves.

Short sight (Pg. 132)

A short-sighted person sees near objects clear but distant objects appear blurred. The image of a distant object is formed in front of the retina because the eyeball is too long or because the eye lens cannot be made thin enough. The problem is that the angle of incidence doesn't enter from a large enough angle. A diverging spectacles lens corrects the problem. It diverges the light before it enters the eye, to give an image on the retina.

Vacuum

A space from which all the air has been removed.

Bimetallic strip

A strip made of two equal lengths of two different metals, such as copper and iron, riveted together so that they cannot move separately; and bends at a specific way when change in temperature occurs. Used in fire alarms. Copper expands more than iron, therefore it bends toward the side of the iron strip.

Principle of conservation of energy

Energy cannot be created or destroyed; it is always conserved. It can be transferred or transformed into another form. It usually ends up as heat energy.

Pitch

A tone's experienced highness or lowness; depends on frequency. Higher frequency = higher pitch Lower frequency = lower pitch

Momentum

A useful quantity to consider when bodies are involved in collisions and explosions. It is defined as the mass of the body multiplied by its velocity and is measured in kilogram metre per second (kg m /s) or newton second (N s). Momentum = mass x velocity

Distance time graph

A visual representation of the speed of an object. The slope/gradient of a distance-time graph represents the velocity of the body. Y - axis : Distance (m) X - axis : Time (secs)

Transverse waves (Chapter. 25)

A wave in which the particles of the medium move perpendicularly to the direction the wave is traveling.

Longitudinal wave (Pg. 140)

A wave in which the vibration of the medium is parallel to the direction the wave travels. A longitudinal wave can be sent along a spring, stretched out on the bench and fixed at one end, if the free end is repeatedly pushed and pulled sharply, compressions and rarefactions will travel along the spring.

Variable resistors

Also called potentiometers, are used in electronics to control variables such as volume and other controls. Variable resistors that take larger currents are useful in laboratory experiments. These consists of a coil of constantan wire (an alloy of 60% copper, 40% nickel) wound on a tube with a sliding contact on a metal bar above the tube. It may be used as a rheostat (when in series) for changing the current in a circuit, only one end connection and the sliding contact are then required. Rheostat can also act as a potential divider (when in parallel) for changing the p.d. applied to a device; all three connections are then used.

Heat energy

Also called thermal or internal energy and is the final fate of other forms of energy. It is transferred by conduction (through objects), convection (through air) or radiation.

Real image

An image which can be produced on a screen and is formed by rays that actually pass through it (e.g. pinhole camera).

Magnification

An increase in the apparent size of an object. Linear magnification (m) = height of image / height of object Linear magnification (m) = distance of image from lens / distance of object from lens

Expansion

An increase in the volume of an object due to an increase in average kinetic energy (temperature), causing vibration and particles moving apart. Expansions are used in... Opening tight metal lids by adding hot water to surrounding. Contractions are used in... Installing gear wheels onto axles by shrinking axles using liquid nitrogen at -196 degree Celsius (axles expand back to original size after returning to room temperature and tightens the gear wheels). Precautions against expansions: Extra space between joints (e.g. railroads and bridges) to allow expansion to happen without cracking the structure.

Electrons, insulators and conductors

An insulator has all its electrons bound firmly to its atoms. A conductor has some electrons that can move freely from atom to atom. An insulator can be charged by rubbing because the charge produced cannot move from where it was produced, i.e. the electric charge is static. A conductor will only become charged if it is held with an insulating handle, otherwise electrons are transferred between the conductor and the ground via the person's body. Insulator examples : Plastics, polythene, cellulose acetate, perspex and nylon. Conductor examples : Metals and carbons. Therefore, insulators are more easily charged.

Newton's First Law

An object at rest wants to stay rest and an object in motion wants to stay in motion with the same speed, and in the same direction unless acted upon by an unbalanced force. A body stays at rest, or if moving it continues to move with uniform velocity, unless an external force makes it behave differently. Newton's First Law = Law of Inertia Mass of a body measure its inertia Heavier weight objects = higher inertia = requires higher force to stop its motion or move it.

Infrared radiation

Bodies detect IR by its heating effect on the skin, it's also called radiant heat or heat radiation. Anything which is hot but not glowing, i.e. below 500 degree Celsius emits IR alone. At about 500 degree Celsius a body becomes red hot and emits red light as well as IR. At 1,500 degree Celsius, bodies are white hot and radiate IR and white light (e.g. lamp filaments). Inferred sensors are used on satellites and aircraft for weather forecasting and monitoring of land use, and remote controls.

Virtual image

Cannot be formed on a screen and is produced by rays which seem to come from it but do not pass through it (e.g. mirror images). The real rays are the ones that actually reflects off from the mirror from the original object. The virtual rays are the ones that makes you think that there is another object which you are looking at.

Renewable energy resources

Clean and environmentally friendly energy that cannot be exhausted and are generally non-polluting.

Natural convection currents

Coastal breezes In the day the temperature of land increases quicker than the seas. The hot air above the land rises and is replaced by cold air from the sea. A breeze from the sea results. At night, the opposite happens. The sea has more heat to lose and cools more slowly. The air above the sea is warmer than that over the land and a breeze blows from the land. Gliding, including hang-gliders depend on hot air currents, called thermals.

Geothermal energy

Cold water is pumped down a shaft into hot rocks in the ground and comes back up as steam. The steam can drive turbines and generate electricity or to heat buildings. These are mostly located in USA, New Zealand, and Iceland. The problem with this is that it is geographically limited.

Convection in liquids and air

Convection is the usual method by which thermal energy (heat) travels through fluids such as liquids and gases. Or heat energy transferred due to difference in density (only gases and liquids). Convection is the flow of heat through a fluid from places of higher temperature to places of lower temperature by movement of the fluid itself. When being heated, upward water currents are created, these are called the convection currents. The molecules arise because it expands, and become less dense, so they are forced to rise. Same as the density of air molecules decreases and rises. Convection of air helps heating up buildings or radiating heat. 1. Warmer regions are less dense, rise upwards, pushing down the denser cold regions 2. Occurs due to bulk movement of particles 3. Creates convection current as mentioned above (water currents...etc).

Spectacles

Converging in lens in the eye will form a real inverted image on the retina. Since an object normally appears upright, the brain must invert the image.

Magnifying glass

Converging lens gives an enlarged, upright virtual image. The fatter (more curved) a converging lens is, the shorter its focal length and the more it magnifies. Too much curvature, however, distorts the image.

Displacement (Δd) (vector)

Distance moved in a stated direction. It is a vector, unlike distance which is a scalar.

Electric heating

Domestic appliances such as electric fires, cookers, kettles and irons the 'elements' are made from Nichrome wire. This is an alloy of nickel and chromium which does not oxidise (and so become brittle) when the current makes it red hot. The elements in radiant electric fires are at red heat (around 900 degree Celsius) and the radiation they emit is directed into the room by polished reflectors. In convector types the element is below red heat (about 450 degree Celsius) and is designed to warm air which is drawn through the heater by natural or forced convection. In storage heaters the elements heat fire-clay brick during the night using 'off-peak' electricity. On the following day these cool down, giving off the stored heat to warm the room. Check out this picture using this link: https://www.google.com/search?safe=strict&rlz=1C1CHBF_zh-TWSG841SG841&biw=1536&bih=754&tbm=isch&sa=1&ei=1IqpXNaANcTVz7sPueOXiAM&q=electric+heating+physics&oq=electric+heating+physics&gs_l=img.3...8671.11676..11785...0.0..0.54.1019.24......1....1..gws-wiz-img.......0j0i67.Q-5prXvp3Vs#imgrc=lrnPoM4YueAv4M:

Good absorbers and bad absorbers

Dull black surfaces Good absorbers of radiation, good emitter/radiator of radiation (loses heat fast), but poor reflector Cooling fins on the heat exchangers at the back of a refrigerator are painted black so that they lose heat more quickly. White shiny surfaces Poor absorbers of radiation, Poor emitter/radiator of radiation(keeps heat well), Good reflector By contrast, saucepans that are polished are poor emitters and keep their heat longer.

Nuclear energy

E = mc^2 Einstein predicted that if the energy of a body changes by an amount E, its mass changes by an amount m.

Seismic waves

Earthquakes produce both longitudinal waves (P - waves) and transverse waves (S - waves) that are known as seismic waves. These travel through the Earth at speeds of up to 13,000 m / s. When seismic waves pass under buildings, severe structural damage may occur. However, the seismic energy can be transmitted to the water and produce tusnami waves as well, which may travel for very large distances across the ocean. When tsunami wave approaches shallow coastal waters, it slows down and its amplitude increases, which can lead to massive coastal destruction.

Dangers of electricity

Electric shocks occurs if current flows from an electric circuit through a person's body to earth. Happens if there is damaged insulation or faulty wiring. Size of the current (not voltage) and the length of time determines the strength of an electric shock. Damp conditions increase the severity of an electric shock because water lowers the resistance of the path to earth; wearing shoes with insulating rubber soles or standing on a dry insulating floor increases the resistance between a person and earth and will reduce the severity of an electric shock. To avoid the risk of getting an electric shock: Switch off the electrical supply. Use plugs that have an earth pin and a cord grip (rubber/plastic case). Do not allow appliances or cables to come into contact with water. Do not have long cables trailing across a room, under a carpet that is walked over regularly, as it gets damaged. Take particular care when using electrical cutting devices (such as hedge cutters) not to cut the supply cable. To reduce the risk of fire through overheated cables, the maximum current in a circuit should be limited by taking these precautions: Use plugs that have the correct fuse. Do not attach too many appliances to a circuit. Don't overload circuits by using too many adapters Appliance such as heaters use large amounts of power (and hence current), so do not connect them to a lighting circuit designed for low current use. Damaged insulation => electric shock and fire risk Overheated cable => fire risk Damp conditions => increased severity of electric shocks

P3

Electricity

Radio waves

Electromagnetic waves with the longest wavelengths and lowest frequencies. Wavelengths of 2 to 10 kilometer. Used for carrying sound, pictures, and other information over long distances. 1. Long, medium and short waves (2 km - 10 meters) They are also reflected by layers of electrically charged particles in the upper atmosphere (the ionosphere), which makes long-distance radio reception possible. 2. VHF (very high frequency) and UHF (ultra high frequency) waves (10 meters - 10 cm) These shorter wavelength radio waves need a clear straight-line path to the receiver. They are not reflected by the ionosphere. They are used for local radio and for televisions. 3. Microwaves (wavelengths of a few cm) Is a type of radiowaves Used for international telecommunications and television relay via geostationary satellites and for mobile phone networks via microwave aerial towers and low-orbit satellites. The microwave is transmitted through the ionosphere by dish aerials, amplified by the satellite and sent back to a dish aerial in another part of the world.

Velocity in vacuum

Falling speed of two free falling objects with different weight in a vacuum remains the same, due to no air friction affecting the speed.

Faraday's Law

Faraday suggested that a voltage is induced in a conductor whenever it 'cuts' magnetic field line, i.e. moves across them, but not when it moves along them or is at rest. If the conductor forms part of a complete circuit, and induced current is also produced. Voltage increases with increases of: The speed of motion of the magnet or coil The number of turns on the coil The strength of the magnet The law: The size of the induced p.d. is directly proportional to the rate at which the conductor cuts magnetic field lines.

Florescent strips

Five times more efficient than filament lamps, and may last 3,000 hours. Costs more to install but running costs are less. When turned on, the mercury vapour emits invisible ultraviolet radiation which makes the powder on the inside of the tube fluoresce (glow), i.e. visible light is emitted. Different powders give different colours.

Fleming's Left Hand Rule

Flemings left hand rule is were your left hand first finger = the direction of field Your second finger = which ways the current is going And your thumb = the force the magnet going in

Convex lenses (camera & human eyes)

For a distant object that is placed more than twice the focal length from the lens, the image is: Inverted Diminished Real

Boiling

For a pure liquid boiling occurs at a definite temperature called its boiling point and is accompanied by bubbles that form within the liquid; containing the gaseous or vapour form of the particular substance. Latent heat is needed in both evaporation and boiling and is stored in the vapour, from which it is released when the vapour is cooled or compressed and changes to liquid again. Points: 1. Occurs at boiling point 2. Throughout the liquid 3. Takes energy in to occur (endothermic) 4. No cooling 5. Rapid process

Like charges

For example (+) and (+) / (-) and (-) repel each other.

Unlike charges

For example (+) and (-) / (-) and (+) attract each other.

Electron current

Negative to positive.

Limits of audibility

Humans hear only sounds with frequencies from about 20 Hz to 20,000 Hz. These are the limits of audibility; the upper limit decreases with age.

Newton's Third Law

If a body A exerts a force on body B, then body B exerts and equal but opposite force on body A. E.g. If a person exerts 10 newtons toward a wall, then the wall is exerting 10 newtons back to him simultaneously too.

North and south poles

If a magnet is supported so that it can swing in a horizontal plane it comes to rest with one pole, the north-seeking or N pole, always pointing roughly towards the Earth's north pole. A magnet can therefore be used as a compass.

Electrons

Negatively charged subatomic particles.

Biomass (vegetable fuels)

Include cultivated crops, crop residues, natural vegetation, trees grown for their wood, animal dung and sewage. Biofuels such as alcohol (ethanol) and methane gas are obtained from them by fermentation using enzymes or by decomposition by bacterial action in the absence of air. Liquid biofuels can replace petrol, although they have up to 50% less energy per litre, they are lead and sulfure free and so cleaner. Biogas is a mixture of methane and carbon dioxide with an energy content about two thirds that of natural gas. In developing countries it is produced from animal and human waste in digesters and used for heating an cooking.

Fossil fuels

Including coal, oil and natural gas, formed from the remains of plants and animals which lived millions of years ago and obtained energy originally from the Sun. These pollutes the atmosphere with harmful gases such as CO2 and SO2 after being burned and used.

Temperature

Increase in temperature = increase in average kinetic energy in molecules (gas in this scenario) = it will increase gas pressure if the volume doesn't increase due to the more frequent collision of gas back and forth onto the container walls. Scale of temperature. A scale and unit of temperature are obtained by choosing two temperatures, called the fixed points, and dividing the range between them into a number of equal divisions or degrees. On the Celsius scale, the lower fixed point is the temperature of pure melting ice, and is taken as 0 degree Celsius. The upper fixed point is the temperature of the steam above water boiling at normal atmospheric pressure, 10^5 Pa, and is taken as 100 degree Celsius.

Thermistor

Increase of temperature increases the resistance of metals, as for the filament lamp, but it decreases the resistance of semiconductors. The resistance of semiconductor thermistors decreases if their temperature rises. If a resistor and a thermistor are connected as a potential divider, the p.d. across the resistor increases as the temperature of the thermistor increases; the circuit can be used to monitor temperature, for example in a car radiator.

Magnetic materials

Iron, steel, nickel, and cobalt, which are also called ferro-magnetics.

Clinical thermometer

Is a special type of mercury-in-glass thermometer used by doctors and nurses. Its scale only extends over a few degrees on either side of the normal body temperature of 37 degree Celsius, i.e. it has a small range. Because of the very narrow capillary tube, temperatures can be measured very accurately, in other words, the thermometer has a high sensitivity.

Atom

Is normally electrically neutral, i.e. has no net charge because of the balanced amount of protons and electrons.

Vacuum flask

Keeps hot liquids hot or cold liquids cold efficiently because it is very difficult for heat to travel into or out of the flask. Flask parts : Stopper on the top Case on the outside Felt pad to support vacuum space between case (most outer layer) and two silvered surfaces of the double-walled glass vessels (second and third layer, three layers in total).

Thermostat

Keeps the temperature of a room or an appliance constant. Using the same method as bimetallic strip, to trigger control knob and control the heating system. Usually used to break circuits to switch off heaters. Control knob changes the distance between the strip and circuit, so when the knob is adjusted to a higher temperature, the strip would have to bend more to close the circuit, in order to turn on the heater.

Light pipes and optical fibres

Light can be trapped by total internal reflection inside a bent glass rod and 'piped' along a curbed path. A single, very thin glass fibre behaves in the way. If several thousand such fibres are taped together, a flexible light pipe is obtained that can be used by doctors as an endoscope to obtain image from inside the body, or by engineers to light up some awkward spot for inspection. The latest telephone 'cables' are optical (very pure glass) fibres carrying information as pulses of laser light.

Other forms of energy

Light energy, electromagnetic radiation, sound energy and nuclear energy.

Liquid pressure

Liquid pressure = PGH (Density of water x Gravitational pull x Height or depth. Pressure depends on the density of the liquid. The denser the liquid, the greater the pressure at any given depth. Pressure in liquid increases with depth. Pressure at one depth acts equally in all directions. A liquid finds its own level. Usage : Hydraulic machines, hydraulic jack (DT).

Matter

Made up of tiny particles or molecules which are too small for us to see directly.

Magnetism of iron and steel

Magnetism induced in iron is temporary. However, magnetism induced in steel is permanent. Magnetic materials such as iron that magnetise easily but readily lose their magnetism (are easily demagnetised) are said to be soft. Those such as steel that are harder to magnetise than iron but stay magnetised are hard.

Calibrated

Marked with a linear scale. E.g. A thermometer now has a linear scale, in other words it has been calibrated or graduated.

Density

Mass per unit volume of a substance. Calculated in rho (p) Density = mass / volume P = m / V SI unit of density is kg / cubic metre (m3) G / cm3 Aluminium 2.7 Copper 8.9 Iron 7.9 Gold 19.3 Glass 2.5 Wood 0.80 Ice 0.92 Polythene 0.90 G / cm3 Pure water 1.0 Mercury 13.6 KG / m3 Air 1.3 Hydrogen 0.09 CO2 2.0

Conductors

Materials that can transfer electricity and heat energy efficiently. Usages : saucepans, boilers, and radiators.

Insulators

Materials that do not conduct heat nor electricity well. E.g. Materials that trap air, wool, felt, fur, feathers, polystyrene foam, fibreglass, are also very bad conductors.

P5

Matter & Thermal Physics

Distance (s) (scalar) | meters & kilometers

Measurement of the actual path covered.

Thermocouple

Measures high/low temperatures, that vary rapidly, localized/small site/point, in controlled systems. Made up of a galvanometre with 4 wired of 2 different metals. Photo link https://www.google.com/search?safe=strict&biw=1440&bih=820&tbm=isch&sa=1&ei=M5W-XLTxH9zWz7sP3PaEmAo&q=thermocouple+diagram+igcse&oq=thermocouple+diagram+igcse&gs_l=img.3..0j0i8i30.721.1808..2858...0.0..0.46.227.6......1....1..gws-wiz-img.......0i30j0i5i30.b4ZpNd1jodo#imgrc=7QGLxeghLmqhjM: Two junctions at different temperatures, one hot one cold. Temperature difference causes e.m.f./voltage/current. One junction at known temperature for calibration. Reading of galvanometre changes with temperature.

Conduction and the kinetic theory

Metals have a large number of free electrons, as a part being heated, another part gets vibrates fast too, therefore, good conductors have free electrons that can pass on heat energy fast.

Explosions

Momentum is conserved in an explosion such as occurs when a rifle is fired. Before firing, the total momentum is zero since both rifle and bullet are at rest. During the firing the rifle and bullet receive equal but opposite amounts of momentum so that the total momentum after firing is zero. For example, if a rifle fires a bullet of mass 0.01 kg with a velocity of 300 m/s. 0.01 kg x 300 m/s = 3 kg m/s which means backward momentum of rifle = 3 kg m/s

Gamma rays

More penetrating and dangerous than X-rays. They are used to kill cancer cells and also harmful bacteria in food and on surgical instruments.

P1

Motions and Mechanics

Constant speed

Moving at a steady rate over time. Meters / second remains constant.

Gamma rays

Not charged, nor has a relative mass. Its nature is electromagnetic radiation of very short wavelength. These are the most penetrating and are stopped only by thick lead or concrete. They ionise a gas even less than beta-particles and are not deflected by electric and magnetic fields. They give interference and diffraction effects and are electromagnetic radiation travelling at the speed of light. Their wavelengths are those of very short X-rays, from which they differ only because they arise in atomic nuclei whereas X-rays come from energy changes in the electrons outside the nucleus. Cobalt (Co-60) emits γ rays and β particles but can be covered with aluminium to provide pure γ rays

Background radiation

Nuclear radiation that occurs naturally in the environment, emitted by radioactive materials in rocks, the air and our bodies, and party by cosmic rays form outer space.

Frequency (f) (Chapter. 25)

Number of oscillations per unit time. Or number of complete waves generated per second. Measured in hertz (Hz). f = λ / V

Luminous sources

Objects that emit light (e.g. sun & electric lamps).

Non-luminous sources

Objects that reflect light emitted by luminous objects.

Newton's Second Law

One Newton is defined as the force which gives mass of 1 kg an acceleration of 1m/s2. 1 Newton causes a 1 kg object to move at 1 m/s Force = Mass x Acceleration

Law of moments

Or so called law of the lever, refers to when a body is in equilibrium the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point. There is no net moment on a body which is in equilibrium. First class Object on left, fulcrum in centre, effort on right. Second class Fulcrum on left, object in centre, effort on right. Third class Fulcrum on left, effort in centre, object on right

Phase

Parts or positions of a wave that has the same direction and placement in the pattern. For example, crests on the waves are in phase. Crest on the upper part and bottom part are not in phase.

Effciency

Percentage of the energy supplied to it that is usefully transferred. Efficiency = (Useful energy output / total energy input) x 100%

Magnetic poles

Poles are the place in a magnet to which magnetic materials, such as iron filings, are attracted. They are near the ends of a bar magnet and occur in pairs of equal strength.

Refraction effects

Pool looks shallower than it is, pencil looks as if it was bent at the water surface.

Conventional current

Positive to negative.

Protons

Positively charged subatomic particles.

Mechanical (Chapter. 25)

Produced by a disturbance, such as a vibrating object, in a material medium and transmitted by the particles of the medium vibrating to and fro.

X-ray

Produced when high-speed electrons are stopped by a metal target or not penetrable target (for electrons) in an X-ray tube. X-rays have smaller wavelengths than UV.

Kaleidoscope

Produces patterns using the images formed by two plane mirrors, the patterns change as the object moves. You only have to remember what it looks like and that the mirrors are placed at the same angle between each (60 degree)

Radiation

Radiation is the third way in which heat can travel, but unlike conduction and convection both requiring matter to be present, radiation can occur in vacuum. Particles are not involved. Radiation is the way heat reaches us from the sun. Radiation has all the properties of electromagnetic waves. Radiation is the flow of heat from one place to another by means of electromagnetic waves. Radiation is emitted by all bodies above absolute zero and consists mostly of infrared radiation. But light and ultraviolet are also present if the body is very hot.

Radioactive decay

Radioactive atoms have unstable nuclei which change or 'decay' into atoms of a different element when they emit α or β particles. The decay is spontaneous and cannot be controlled; also it does not matter whether the material is pure or combined chemically with something else. Alpha decay (nucleon number -4, proton number -2) An α particle is a helium nucleus, having two protons and two neutrons, and when an atom decays by emission of an α particle, its nucleon number decreases by four and its proton number by two. For example, when radium of nucleon number 226 and proton number 88 emits an α particle, it decays to radon of nucleon number 222 and proton number 86. 226/88 Ra => 222/86 Rn + 4/2 He Beta decay (+1 proton) If a β decay a neutron changes to a proton and an electron. The proton remains in the nucleus and the electron is emitted as a β particle. The new nucleus has the same nucleon number, but its proton number increases by one since it has one more proton. Radioactive carbon, called carbon - 14, decays by β emission to nitrogen: 14/6 C => 14/7 + 0/-1 e Gamma emission After emitting an α particle, or β- or β+ particles, some nuclei are left in an 'excited' state. Rearrangement of the protons and neutrons occurs and a burst of γ-rays is released.

Light waves

Red light has the longest wavelength, while violet light has the shortest wavelength. The amplitude of a light wave is greater the higher the intensity of the source; in the case of light the greater the intensity the brighter it is. Light of one colour is called monochromatic light. The frequency of the light decides its colour. Red light has a lower frequency since it has longer wavelength.

Diffuse reflection

Reflection that occurs when parallel rays of light hit a rough surface and all reflect into different directions, irregularly.

Regular reflection

Reflection that occurs when parallel rays of light hit a smooth surface and all reflect off regularly.

Alpha particles

Relative charge of +2. Relative mass of 4 a.m.u. Its nature is helium nucleus with 2 protons, 2 neutrons. Can be stopped by a thick sheet of paper and have a range in air of only few centimetres since they cause intense ionisation (10^5 ion pairs per cm) in a gas due to frequent collisions with gas molecules. They are deflected by electric and strong magnetic fields in a direction and by an amount which suggests they are helium atoms minus two electrons, i.e. helium ions with a double positive charge. From a particular substance, they are all emitted with the same speed (about 1 / 20th of that of light). Americium (Am-24 1) is a pure α particle source.

Beta particles

Relative charge of -1. Relative mass of 1/1840 a.m.u. Its nature is electron. These are stopped by a few millimetres of aluminium and some have a range in air of several metres. Their ionising power (100 ion pairs per cm) is much less than that of alpha particles. As well as being deflected by electric fields, they are more easily deflected by magnetic fields. Measurements show that beta particles are streams of high-energy electrons, like cathode rays, emitted with a range of speeds up to that of light. Strontium (Sr-90) emits β particles only.

Other thermometers

Resistance thermometer Uses the fact that the electrical resistance of a platinum wire increases with temperature. It can measure accurately in the range from -200 degree Celsius to 1,200 degree Celsius. Thermistor Can measure from -5 to 70 degree Celsius. Constant - volume gas thermometer Thermochromic liquids Change colour with temperature have a limited range around room temperatures.

Non-renewable energy resources

Resources that cannot be replaced by natural processes quickly as they're used. Advantages: 1. Their high energy density (i.e. they are concentrated sources) and the relatively small size of the energy transfer device (e.g. a furnace) which releases their energy. 2. Their ready availability when energy demand increases suddenly or fluctuates seasonally.

Velocity time graphs

Shows how the speed or velocity of an object changes over time. Y - axis : Velocity (m/s) X - axis : Time (secs)

Simple d.c. generator (dynamo)

Similar to a.c. generator but the slip rings are replaced by a commutator. The brushes are arranged so that as the coil goes through the vertical, changeover of contact occurs from one half of the split ring of the commutator to other. But it is when the coil goes through the vertical position that the voltage induced in the coil reverses, so one brush is always positive and the other negative.

Principal focus

So called focal point, the point on the principal axis of a lens where light rays parallel to the principal axis converge after refraction.

Solar energy

Solar panels convert light into electricity. Solar thermal energy plants can also convert light into heat for heating up water (up to 70 degree Celsius). Both look similar, but have quite different functions. Solar furnace or a large curved mirror focuses the sin's rays on to a small area and can heat up to 3,000 degree Celsius.

Magnetisation

Solenoids can be used to magnetise and demagnetise magnetic materials. Demagnetisation can be caused by... Dropping or heating a magnet, hammering a magnet. Magnetisation can be done by stroking a magnetic material several times in the same direction with one pole of a magnet.

Kinetic theory of matter

Solids Solid molecules are close together and the have strong attraction forces. Therefore they vibrate to and fro about a fixed positions. Has definite shape and volume and unable to move around freely. Liquids Liquid molecules are slightly further apart than in solids, but still close enough together to have a definite volume. Has no definite shape but has a definite volume and can move around. Gases Gas molecules are much further apart than in solids or liquids (about ten times) so they are much less dense and can be squeezed into a smaller space. There irregular motion represents Brownian motion. Has no definite shape nor volume and can move around freely at a estimated speed of 500 m/s at 0 degree Celsius.

Ultrasonics

Sound waves with frequencies above 20,000Hz. Their frequency is too high to be detected by the human ear but they can be detected electronically. Ultrasonic waves partially or totally reflect from surfaces at which the density of medium changes. Ship with sonar can determine the depth of a shoal of fish or the sea bed. In medical ultrasound imaging, it is used in clinics to determine the sex of an unborn baby, as an ultrasonic transmitter / receiver is scanned over the mother's abdomen and a detailed image of the fetus is built up.

Specific latent heat of fusion

Specific latent heat of fusion of a substance is the quantity of heat needed to change unit mass from solid to liquid without temperature change. When a solid is melting, the heat supplied does not cause a temperature rise; heat is added but does not cause a temperature rise in the object. E.g. The temperature of a well-stirred ice-water mixture remains at 0 degree Celsius until all the ice is melted. Latent heat is measured in J / kg or J / g. In general, the quantity of heat Q to change a mass m from solid to liquid is given by... Q = m x l(f) Water: To evaporate : 2260 kj / kg To freeze : 334 joules / gram

Speed of sound

Speed of sound in air = distance travelled by the sound / time taken. V = d / t

Driving and car safety

Stopping distance = thinking distance + braking distance Crumple zones at the front a rear collapse in such a way that the K.E. is absorbed gradually. Extensible seat belts exert a backwards force (of 10,000 N or so) over about 0.5 m. Air bags in some cars inflate and protect the driver from injury by the steering wheel. These are secondary safety devices which aid survival in the event of an accident. Primary safety factors help to prevent accidents and depend on the car's roadholding, brakes, steering, handling and above all on the driver since most accidents are due to driver error. The chance of being killed in an accident is about five times less if seat belts are worn and head restraints are installed.

Constant temperature

Temperature stays the same for these changes of state: 1. As heat energy given is not used to increase to kinetic energy 2. Used to break / overcome intermolecular forces of attraction between molecules. (The melting object's temperature doesn't change, only the temperature of the surrounding environment does). 3. Used to increase potential energy of the molecules. 4. This heat energy for state changes is known latent heat.

Energy (E)

The ability and capacity to do work. Measured in Joules (J) Energy = Coulomb x Volts E = Q x V Energy = Current x time x voltage E = ItV

Penetrating power

The ability of radiation to pass through matter.

Angle of incidence

The angle between the incident ray and the normal.

Angle of reflection

The angle between the normal and reflected ray.

Laws of Refraction

The bending of a wave as its speed changes when passing at an angle from one medium to another. Shallow region = shorter wavelength Deeper region = longer wavelength Hence waves travel more slowly in shallow water. Facts : 1. Ray of light is bent towards the normal when it enters an optically denser medium at an angle (e.g. air => glass). Less dense => Denser medium, towards. 2. Ray of light is bent away from the normal when it enters an optically less dense medium (e.g. glass => air) Denser => Less dense medium, away.

Laws of Reflection

The bouncing back of a wave when it hits a surface through which it cannot pass. Rule : Angle of incidence = Angle of reflection. Normal is the line perpendicular to the reflecting surface. Angle of incidence is the angle close to where the light hits the surface. Angle of reflection is the angle close to where the light bounces off the surface. Incident ray, Normal, Reflected Ray lie on the same plane.

Optical centre (C)

The centre of a lens.

Acceleration (a) (vector) | m/s^2

The change of velocity in unit time. Acceleration = change of velocity / time taken for change

Terminal velocity

The constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity. When air resistance equals to the weight of the falling object acting downwards.

Ohm's Law

The current in a circuit equals the voltage difference divided by the resistance.

Metallic conductors

The current in a metallic conductor is directly proportional to the P.D. across its ends if the temperature and other conditions are constant.

Potential difference (P.D.) (V)

The difference in electrical charge between two points in a circuit expressed in volts. Evidently the p.d. across a device affects the rate at which it transfers electrical energy. Measured in volts. Measured by a voltmeter in a parallel circuit. Potential difference (Volts) = Current (I) x Resistance (R) V = I x R Volts = Energy / Coulomb V = E / Q Volts = Watts / Ampere V = E / A 1 volt = 1 joule per coulomb (1V = 1 J/C) The P.D. between two points in a circuit is 1 volt if 1 joule of electrical energy is transferred to other forms of energy when 1 coulomb passes from one point to the other.

Alternative current (AC)

The direction of flow reverses regularly. Generators produce AC. Frequency of AC is the number of complete alternations or cycles in 1 second. In the example picture, there are two cycles and let's said it happened in 1 second. Then it means the frequency is 2 Hz. For example, the mains supply in the UK is a.c. of frequency 50 Hz, each cycle lasts 1 / 50th of a second.

Lenz's Law

The direction of the induced current is such as to oppose the change causing it. When magnet approaches coil... The side of the magnet closest to the coil becomes North and so is the side of the coil close to the magnet. When magnet is withdrawn from the coil... The side of the magnet closest to the coil is still north but the side of the coil close to the magnet becomes south pole.

Ray

The direction of the path which light is travelling. A beam may be parallel, diverging (spreading out), or converging (getting narrower).

Wavelength (λ) (Chapter. 25)

The distance from one peak to the next in a wave. Measured in meters (m). The distance between successive crests. λ = f x V

Speed for waves (v) (Chapter. 25)

The distance moved in the direction of travel of the wave by a crest or any point on the wave in 1 second. V = λ x f

Velocity (Δv) (vector) | m/s

The distance moved in unit time in a stated direction. Velocity = distance moved in a stated direction / time taken Δv = s/t in a direction Velocity = displacement / time taken Δv = a/t Average velocity = (Initial velocity + Final velocity) / 2 Average Δv = (u+v)/2

Speed (v) (scalar) | m/s & km/hr

The distance moved in unit time. Average Speed = distance / time taken v = s/t

Electromagnetic induction

The effect of producing electricity from magnetism was discovered in 1831 by Faraday. It led to the construction of generators for producing electrical energy in power stations. Two ways to investigate: Straight wire and U-shaped magnet. When straight wire is moving upwards or downwards, there is a deflection on the meter, indicating an induced in the wire. Bar magnet and coil. When a magnet is pushed into a solenoid, a current is induced.

Direct current (DC)

The electrons flow in one direction only. Both generators and battery can produce DC.

Kinetic energy (K.E.)

The energy an object has due to its motion. The faster an object moves, the more K.E. it has. KE = 1/2 x Mass x Velocity to the second power

Electrical energy

The energy of electric charges. Produced by energy transfers at power stations and in batteries, Examples : Power stations and batteries.

Nuclear fuels

The energy released in a nuclear reactor from uranium, found as an ore in the ground, can be used to produce electricity. Nuclear fuels do not pollute the atmosphere, but they do generate radioactive waste materials with very long half-lives.

Potential energy (P.E.)

The energy stored in an object because of its position or condition. Usually stored in the form of gravitational potential energy. Others included elastic potential energy for example on a bow. PE = Mass x Gravitational pull x Height

Chemical potential energy

The energy stored in the chemical bonds of a substance. Examples: Food, fuels, coal, wood, gas, chemicals in batteries.

Electromagnetic radiation

The energy transferred through space by electromagnetic waves. A kind of radiation including radiowaves, microwaves, visible light, infrared, ultraviolet, X-rays and Gamma rays in which electric and magnetic fields vary simultaneously. Because of its electrical origin, its ability to travel in a vacuum and its wave-like properties, electromagnetic radiation is regarded as a progressive transverse wave. Properties: 1. All types of electromagnetic radiation travel through a vacuum at 300,000 km/s. 2. They exhibit differences, diffraction and polarisation, which suggests they have a transverse wave nature. 3. They obey the wave equation. 4. They carry energy from one place to another and can be absorbed by matter to cause heating and other effects. The higher the frequency, and the smaller the wavelength of the radiation, the greater is the energy carried, i.e. gamma rays are more 'energetic' than radio waves. This is shown by the photoelectric effect in which electrons are ejected from metal surfaces when electromagnetic waves fall on them. As the frequency of the waves increases so too does the speed (and energy) with which electrons are emitted.

Amplitude (a) (Chapter. 25)

The height of a crest or the depth of a trough measured from the undisturbed position of what is carrying the wave, such as a rope.

Projectiles

The horizontal and vertical motions of a body when falling are independent and can be treated separately. Vertical accelerations (due to gravity) of two falling objects are equal, even if one is falling sideways.

Hooke's Law

The law refers to how the extension of springs are proportionate to the stretching force. Extension α stretching force K = F / x Force constant = force x extension

Principal axis

The line through optic centre (C) at right angles to the lens. When object is close, the ray is a diverging beam. When object is distant, the ray is almost parallel beam. When object is very distant, the ray will then be parallel beam.

Ohm

The ohm is the resistance of a conductor in which the current is 1 ampere when a voltage of 1 volt is applied across it.

Resultant force

The overall force on a point or object.

Compression

The part of a longitudinal wave where the particles of the medium are close together.

Rarefaction

The part of a longitudinal wave where the particles of the medium are far apart.

Neutrons

The particles of the nucleus that have no charge.

Normal

The perpendicular to the mirror at the point where the incident ray strikes it.

Centre of mass

The point where a body behaves as if its whole mass were concentrated.

Electromotive force (E.M.F.)

The power supplied by the supply per unit current. The energy provided by a cell or battery per coulomb of charge passing through it, it is measured in volts (V).

Evaporation

The process which the energetic molecules close to the surface of a liquid may escape and become gas molecules. Factors 1. Higher temperature = higher rate 2. Larger surface area = higher rate 3. Wind blowing over surface = increase rate 4. Lower humidity = higher rate Points: 1. At any temperature 2. At the surface 3. Only the molecules with the highest KE escape 4. Produces cooling 5. Slow process

Charges

The production of charges by rubbing can be explained by supposing that electrons are transferred from one material to the other. For example, when cellulose acetate is rubbed with a cloth, electrons go from the acetate to the cloth. This leaves the acetate short of electrons, i.e. become positively charged, while cloth becomes negatively charged. Note : Only electrons move, protons remain fixed in the nucleus.

Speed of light

The proof that light travels very much faster than sound is provided by a thunderstorm. Flash of lightning is seen before the thunder is heard. Length of the time lapse is greater the further the observer is from the storm. The speed of light has a definite volume; light does not travel instantaneously from one point to another but takes a certain, very small time. Its speed is about 1 million times greater than that of sound (around 300,000 km / hour).

Brownian motion

The random movement of particles due to unbalanced forces and energy.

Echo

The reflected sound wave

Electric fields

The region of space where an electric charge particle experiences a force due to other charges.

Light dependent resistors (LDRs)

The resistance of some semiconducting materials decreases when the intensity of light falling on them increases. Resistance is low when the environment is bright. Resistance is high when the environment is dark.

Resistivity

The resistivity of a material is numerically equal to the resistance of a 1 m length of the material with cross-sectional area 1 m squared. Resistance = (Resistivity + length) / cross-sectional area

Heat capacity

The specific heat capacity of a substance is the heat required to produce a 1 degree Celsius rise in 1 kg. Heat is measured in joules, and the unit of specific heat capacity is the joule per kilogram per degree Celsius. Thermal capacity of a body is the quantity of heat needed to raise the temperature of the whole body by 1 degree Celsius. Water : 4,200 J / Kg degree Celsius Soil : 800 J / Kg degree Celsius A certain mass of water needs give times more heat than the same mass of soil for its temperature to rise by 1 degree Celsius. High specific heat capacity of water accounts for its use in cooling engines and in the radiators of central heating systems.

Diffraction

The spreading of waves at the edges of obstacles.

Moment of a force

The turning effect of a force. Depends on the size of the force and how far it is applied form the pivot point or fulcrum. Moment of a force = force x perpendicular distance between the force from the fulcrum. The unit is newton metre (Nm) M = F x D

Coulombs (C)

The unit of charge, coulomb (C), is defined in terms of the ampere. Don't mess it up, Q is the symbol for charge, not coulomb. One coulomb is the charge passing any point in a circuit when a steady current of 1 ampere flows for 1 second. That is, 1 C = 1 A s. Q = I x t Coulombs = current x time Q = E / V Coulombs = Energy (J) / Voltage (V)

Newton

The unit of force. 1kg = 9.8Newtons

Charles' Law (gas pressure)

The volume of a fixed mass of gas is directly proportional to its absolute temperature if the pressure is kept constant. The pressure of a fixed mass of gas is directly proportional to its absolute temperature if the volume is kept constant. The pressure of a fixed mass of gas is inversely proportional to its volume if its temperature is kept constant.

Weight

The weight of a body is the force (measure) of gravity on it. The weight of a body of a mass of 1 kg is 9.8 Newtons.

Step-down transformer

There are fewer turns on the secondary than the primary and Vs is less than Vp.

Earth's magnetic field

They run from south to north geographically.

Transformer

Transforms an alternating voltage from one value to another of greater or smaller value. It has a primary coil and a secondary coil wound on a complete soft iron core, either one on top of each other or on separate limbs of the core. An alternating voltage applied to the primary induces an alternating voltage in the secondary. The value of the secondary voltage can be shown, for a transformer in which all the field lines cut the secondary, to be given by: Vs/Vp = NsNp secondary voltage / primary voltage = secondary turns = primary turns

Utraviolet

UV rays have shorter wavelengths than light. They cause fluorescent paints and clothes to glow. This is used on verifying bank notes and documents too. A UV lamp used for scientific or medical purposes contains mercury vapour and this emits UV when an electric current passes through it. Fluorescent tubes also contain mercury vapour and their inner surfaces are coated with special powders called phosphors which radiate light. They also cause sun tan and produce vitamins in the skin but can penetrate deeper, causing skin cancer. Dark skin is able to absorb more UV, so reducing the amount reaching deeper tissues,

Joules

Unit of energy and work. Joules = newtons x metres

Quality

We say the notes differ in quality or timbre. The difference arises because no instrument (except a tuning fork and a signal generator) emits a 'pure' note, i.e. of one frequency. Notes consist of a main or fundamental frequency mixed with others, called overtones, which are usually weaker an have frequencies that are exact multiples of the fundamental. The number and strength of the overtone decides the quality of a note. The waveform of a note played near a microphone connected to a cathode ray oscilloscope (CRO; see chapter 48) can be displayed on the CRO screen.

Critical angle

When light passes at small angles of incidence from an optically dense to a less dense medium (e.g. glass to air), there is a strong refracted ray and a weak ray reflected back into the denser medium. Increasing the angle of incidence increases the angle of refraction. Critical angle is when the angle of refraction is 90 degree (the angle between incidence ray and reflected ray), which causes the refracted ray (the one that exits the mediums) to disappear, and all the incident light is reflected inside the denser medium. The light does not cross the boundary and is said to undergo TOTAL INTERNAL REFLECTION CRITICAL ANGLE = 90 DEGREE, CREATES TOTAL INTERNAL REFLECTION.

Mutual induction

When the current in a coil is switched on or off or changed, a voltage is induced in a neighbouring coil. Mutual induction is an example of electromagnetic induction. Lets say coil A is the primary (electricity passing through) and coil B is the secondary (neighbouring coil). Switching on the current in the primary sets up a magnetic field and as its field lines 'grow' outwards from the primary they 'cut' the secondary. A p.d. is induced in the secondary until the current in the primary reaches its steady value. When the current is switched off in the primary,

Reverberation

When the reflecting surface is nearer than 15 meters from the source of sound, and the echo joins up with the original sound (which seems to be prolonged).

Uniform acceleration

When the velocity of a body increases by equal amounts in equal intervals of time. The slope/gradient of a velocity-time graph represents the acceleration of the body.

Non-uniform acceleration

When the velocity of a body increases by unequal amounts in equal intervals of time. Graph has a curve line instead of a straight line.

Conservation of momentum

When two or more bodies act on one another, as in a collision, the total momentum of the bodies remains constant, provided no external forces act (e.g. friction). For example a truck of mass 60kg moving with velocity 3m/s collides and couples with a stationary truck of mass 30 kg. The two move off together with the same velocity, find the velocity. Total momentum = (60kg x 3m/s) + (30kg x 0) = 180kg m/s Total momentum after is (60kg + 30kg) x v = 90kg x v Since momentum is not lost 90kg x v = 180 kg m/s or v = 2 m/s

Cooling effect of evaporation

When water evaporates from a surface of an object, it has a cooling effect. As the energetic molecules (who carry more K.N.) escapes and evaporates, it leaves the molecules with less energy (KN) behind. And a lower average of kinetic energy means a lower temperature. Latent heat is obtained by the liquid from its surroundings.

Work

Work = Force x Distance moved in direction of force The work done = the amount of energy transferred.

Power

Work done per second, rate of work. Or the rate at which it transfers energy from one form to another. Power = Work done / time taken Power = Energy transfer / time taken Power = Current x Voltage P = IV

Capacitors

You do not need to know about this for the IGCSE Physics. Check it out on Pg. 174 on your textbook (Duncan Third Edition)

Energy of food

You don't need to know this (bonus) Calories The energy value of a food substance is the amount of energy released when 1kg of it is completely oxidised.

Elastic energy

You don't need to know this (bonus) There are normally a loss of kinetic energy in all collisions, usually to heat energy and to small extent to sound energy. The greater the proportion of K.E. lost, the less elastic is the collision, i.e. the more inelastic it is. In a perfectly elastic collision, K.E. energy is conserved.

Linear expansivity

You don't need to know this for IGCSE The linear expansivity x of a substance is the increase in length of 1 m for 1 degree Celsius rise in temperature. Expansion = linear expansivity x original length x temperature rise

Electrostatic induction

You will have to know how to explain the attraction between uncharged and charged objects. Case 1 In this example, the plate is pulled to the negatively charged plastic rod. When the two objects come closer together, the charge on the rod pushes free electrons to the bottom of the metal plate, making the top of the metal plate positively charged, and bottom layer negatively charged. The top of the plate is nearer the rod than the bottom. Hence the force of attraction between the negative charge on the rod and the positive charge on the top of the plate is greater than the force of repulsion between the negative charge on the rod and the negative charge on the bottom of the plate. The plate is pulled to the rod. Case 2 Sometimes, even a small scrap of paper, which is an insulator, is also attracted by a charged rod. There are no free electrons in the paper but the charged rod pulls the electrons in the paper slightly closer (by electrostatic induction) and so distorts the atoms. In the case of a negatively charged polythene rod, the paper behaves as if it had a positively charged top and a negative charged at the bottom.

Uses of static electricity

a) Flue-ash precipitation An electrostatic precipitator removes the dust and ash that goes up the chimneys of coal-burning power stations. It consists of a charged fine wire mesh which gives a similar charge to the rising particles of ash. They are then attracted to plates with an opposite charge. These are tapped from time to time to remove the ash, which falls to the bottom of the chimney from where it is removed. b) Photocopiers These contain a charged drum and when the paper to be copied is laid on the glass plate, the light reflected from the white parts of the paper causes the charge to disappear from the corresponding parts of the drum opposite. The charge pattern remaining on the drum corresponds to the dark-coloured printing on the original. Special toner powder is then dusted over the drum and sticks to those parts which are still charged. When a sheet of paper passes over the drum, the particles of toner are attracted to it and fused into place by a short burst of heat. c) Inkjet printers In an inkjet printer tiny drops of ink are forced out of a fine nozzle, charged electrostatically and then passed between two oppositely charged plates; a negatively charged drop will be attracted towards the positive plate causing it to be deflected. The amount of deflection and hence the position at which the ink strikes the page is determined by the charge on the drop and the potential difference between the plates; both of these are controlled by a computer. About 100 precisely located drops are needed to make up an individual letter but very fast printing speeds can be achieved.

Dangers of static electricity

a) Thunderclouds carry charges (usually negatively charged at the bottom and positively charged at the top). It repels electrons from the spikes / lightening rod at the top to a metal plate in the ground. The points of the spikes are left with a large positive charge which removes electrons from nearby air molecules, so charging them positively and causing them to be repelled from the spike. This effect, called action at points, results in an 'electric wind' of positive air molecules streaming upwards which can neutralise electrons discharging from the thundercloud in a lightning flash. If a flash occurs it is now less violent and the conductor gives it an easy path to the ground. b) Refuelling, sparks from static electricity may be dangerous when flammable vapour is present. For this reasons, the tanks in an oil tanker may be cleaned in an atmosphere of nitrogen, otherwise oxygen in the air could promote a fire. An aircraft may become charged by 'rubbing' the air. Its tyres are made of conducting rubber which lets the charge pass harmlessly to the ground on landing, otherwise an explosion could be 'sparked off' when the aircraft refuels. c) Computers require similar 'anti-static' conditions as they are vulnerable to electrostatic damage.

Energy losses in a transformer

a) Resistance of windings The windings of copper wire have some resistance and heat is produced by the current in them. Large transformers have to be oil-cooled to prevent overheating. b) Eddy currents The iron core is in the changing magnetic field of the primary and currents, called eddy currents, are induced in it which cause heating. These are reduced by using a laminated core made of sheets, insulated from one another to have a high resistance. c) Leakage of field lines All the field lines produced by the primary may not cut the secondary, especially if the core has an air gap or is badly designed.