physics 3

types of battery

D, C, A, AA, AAA: All have the same voltage (1.5 V). • The chemistry is the same for these battery types, but the amount of the chemicals differs. AAA has the least, D has the most. • Thus they contain different amounts of energy. • More energy means it can move more charge through a 1.5 V difference, so the battery has a longer life.

magnetic force units

Newton

pitch

The frequency of a sound wave is interpreted by our ears and brain as ....

resistance

The resistance of an object (say, a wire) depends on: • The resistivity of the material from which it is made (p). • Its geometry (length, L and cross-sectional area, A) • Its temperature. R=pL/A • Variable: R or r • The longer the wire, the more resistance it offers. • The greater the area (thickness), the less resistance it offers. • An analogy is walking through a crowded hallway. The longer hallway offers more overall resistance, but a wider hallway decreases the opposition to walking.

batteries connected in parallel

both next to each other double lifetime same potential

relationship of Resistance, current and voltage

change in voltage= current*Resistance current=voltage/resistance

wavelength units

meters, m

Charge units

(coulomb, or C)

periodic waves

A series of closely spaced, regular pulses

Relationship of Power loss, resistance & current

As a battery ages, its internal resistance to charge flow builds up in the ionic material, eventually counteracting the voltage available to move charge through itself. They minimize current (I) by raising the voltage (V) • So, they use high voltage power lines for long distances. • We don't want high voltages coming into the house. • So, they use transformers, which raise voltage & lower current on one end. Then they lower voltage & raise current on the other end. • Transformers only work in an AC system

protons

- Holds the smallest possible unit of positive charge

wavelength

- The shortest distance between two particles that are at the same place in their cycle. • Often, the variable is l, and is measured in meters (SI) or other convenient length units.

Fluorescent tubes

A fluorescent tube has an electron source (the cathode) on one end and a positively charged node on the other (the anode). The tube has mercury in vapor form in the space between the nodes. • A high voltage between the nodes causes electrons to jump from cathode to anode (forming a 'cathode ray'). • The electrons strike the mercury atoms' electrons, knocking them up to higher levels. • As high level electrons drop back down, they release the extra energy in the form of ultra-violet light. • This type of tube is used for tanning. • The tube for forming visible light has a fluorescent coating on the inner part of the tube that converts ultra-violet light into visible light.

resonance

A phenomenon that occurs when two objects naturally vibrate at the same frequency singing in the shower If the interacting waves have the correct wavelength (and frequency) within a contained vibrating medium

pipes

A pipe-like instrument works by having sound (pressure) waves within the tube. • In a tube, nodes form at closed ends, and anti-nodes form at open ends. • Wind is blown across the top of a tube or across reeds in the mouth of a pipe, vibrations fill tube • For a tube with one closed and one open end (like a jug or pan flute): • For the fundamental (1 st harmonic), the tube holds one fourth of a complete wave. • The second harmonic is ¾ of a complete wave, the third harmonic is 5/4 of a complete wave, etc. • Longer tubes produce longer wavelengths and thus lower frequencies.

anti-node

A point of maximum amplitude on a standing wave At certain locations on the string, wave pulses traveling in opposite directions constructively interfere, making the string deviate from equilibrium the most.

monopoles

A substance that has only one pole. Electronic monopoles are possible, but magnetic monopoles are not. cutting them in half just creates more north and south

Longitudinal wave

A wave in which the vibration of the medium is parallel to the direction the wave travels

transverse wave

A wave that moves the medium in a direction perpendicular to the direction in which the wave travels

polarized

An atom or molecule can be neutral, but have an uneven distribution of charge. example:H2O

ionized

An atom or molecule can have an unbalanced amount of charge. Positive ions lack one or more electrons, leaving them positive. • Negative ions have an extra electron or two, leaving them negative. have a net charge, so they tend to attract/repel other electrons in an attempt to balance the charge. • This can lead to neutralization and also molecular bonding.

Vibrating strings

transverse waves Imagine a string, fixed at both ends, and under tension. • Producing waves in the string requires energy to displace some part of the string from its straight-line equilibrium position. This energy then travels along the string. . • The speed of wave in the string depends on two properties of the string: • The tension and The density of the string

electrons

'fluid' that is usually transferred is a large number of tiny charged particles called ______ • Holds the smallest possible unit of negative charge. The unit of charge is the same as for the proton, but has opposite sign This is like having positive and negative money. To buy a pencil, instead of giving you a positive dollar, you could give me a negative dollar with the pencil, leaving me $1 poorer and you $1 richer (Proton mass) = 1000*(Electron mass) electron moves

electric field units

(N/C) Newtons / Coulumbs

node

Between each anti-node, the oppositely moving wave pulses destructively interfere, causing the string to not deviate from equilibrium at all

conservation of charge

Charge obeys a fundamental conservation rule: • The net charge in an isolated region is constant. • Rephrased: Charge cannot be created or destroyed unless it is done so in equal quantities of positive and negative charge.

Lightning

Dielectric breakdown occurs during a lightning storm. • The friction between clouds and air transfers charge. One cloud could build up a large positive charge, and the ground below would build up a negative charge in response. • The charge is separated by air (an insulator), so the charge remains separate until the voltage reaches enough to cause the dielectric breakdown of the air. • The electric charge jumps from cloud to ground in the form of a lightning bolt. • The distance of air is less between tall structures and the cloud, so lightning tends to strike them first.

Ionic Air cleaners

Electrons are drawn from a plate and placed onto a nearby brush. leaving the plate positive • Charge (electrons) are on sharp points, so they are motivated to leap off and when dust comes by it leaps onto the dust this makes the dust negative and it gets attracted to the postive plate . • The negative charge jumps to the plate, but then is circulated back to the brush

the water analogies to charge

Example: H2O • Water molecules have a charge effect on each other. This leads to some of the unique properties of water. • Water can be used to neutralize hair that is statically charged. • When ice forms, it expands, unlike most other materials, and so ice floats.

Relationship of Magnetic Force, field strength, charge & speed

FB =B*q*v field strength, charge, and speed are all inversely proportional (all directly proportional to force)

relationship of Electric Force, two charges & distance between

FE=k*q1*q2/r2

frequency units

Hertz (Hz) - waves/second

constructive interference

If both pulses are upright... • ...the energy they contain when they meet adds together on the same side of the string to create a larger upright pulse.

destructive interference.

If one pulse is upright and the other is inverted ... • ...the energy they contain when they meet cancels out, leading to no pulse at all for an instant.

higher harmonics

In general, the nth harmonic has n loops, and its frequency is n*(fundamental frequency)

lightning rod

Lightning rods protect the structures to which they are attached in two ways: • If lightning strikes, the grounded rod transfers it to the ground without passing through the structure, thus avoiding fire or electrical damage. • The rod lowers the chance of a strike to begin with. The charge from the ground tends to flow up to the tip of the rod, which is a sharp point. The charge then escapes from the rod onto nearby particles (coronal discharge), thus dissipating the charge, lowering the voltage, and reducing the chance of a strike.

relationship of Current, charge & time

Like-charges repel, unlike-charges attract. current is the direction of motion of positive charge. Thus, it is opposite the direction of motion of negative charge, and it is electrons that usually move. on battery: As a battery ages, its internal resistance to charge flow builds up in the ionic material, eventually counteracting the voltage available to move charge through itself.

electric force units

Newtons

resistance units

Ohms (Ω)

conductor

Outer electron in each atom is near the energy level required to remove it • Result: Electrons can easily move from atom to atom within the material • Charge can flow through the material (usually a metal) gets cold or hot fast excess charge: the charge can travel through the metal. But it still collects at the surface, where it is able to maximize its distance from the other charges.

insulator

Outer electron is far from the energy level required to remove it • Charge can't move easily through the material example: plastic, rubber, wood, styrofoam, glass excess charge: extra charge sits just at the surface of the material. • The charge can't flow through the material, but it can easily flow along the surface. • Like charge repels, so the charge attempts to distribute itself around the surface.

water analogy

Series Analogy: Water meters at both ends of a water pipe. • Parallel Analogy: A river passing around an island in the stream. Electric: Water Wire :Pipe Charge :Water Current: Current Battery: Pump Voltage: Pressure Switch: Valve Resistance :Turbine Capacitor: Tanks

lifetime & voltage for batteries connected in series or parallel

So imagine a ski resort as an analogy. • If two ski lifts run in parallel: • They both raise the potential by the same amount. • Each does half the work. • For the battery, this means double the battery life. • If two ski lifts run in series: • They double the potential increase. • Each does equal work. • The battery has a normal lifetime.

Relationship of Sound source speed & pitch (Doppler)

Stationary car: The horn sounds the same to observers in front and behind. The sound waves reach the ears at the same frequency. • Moving car: The sound waves are more closely spaced in front. The car catches up to the previous wave before generating a new one. • The sound waves reach the observer in front with a greater frequency, which is interpreted as a higher pitch. • The observer behind the car receives waves at a lower frequency, and hears a lower pitch.

Magnetic field strength units

Tesla, T Gauss, G

Relationship of Wave speed & string density

The density of the string, m - a more massive string has more inertia and is harder to move back toward equilibrium. (m is measured in kg/m.)

Parallel charged plates

The field between the plates contains the electric field, and the field outside the plates is zero. This is useful for many experiments and also everyday devices. Imagine two parallel plates separated by a distance with a flexible dielectric. • Using a battery, charge is transferred from one to the other, and the battery is disconnected. • The voltage between the plates is the same as the battery's original voltage. • Now imagine that the plates are moved closer together. This increases their capacitance. • Since the amount of charge hasn't changed, the voltage between them must decrease. • So detecting a voltage drop means the plates have been pushed together. V=Q/C • This is the principle behind computer keys, for instance. The key press causes a voltage drop which the computer detects.

frequency

The number of cycles that a particular particle goes through in one second. • The variable is usually f, and is measured in cycles per second, or Hertz (Hz). • is the reciprocal of period. A long period is a low frequency, and vice versa.

series

The same current that passes through the first component also passes through the second component.

batteries connected in series

They double the potential increase. • Each does equal work. • The battery has a normal lifetime. one on top of another

Current & voltage in primary and secondary loops in a transformer

Transformers give us the ability to reduce the cost to transmit power by lowering the current with high-voltage wires. The primary side is the power-supply side, and the secondary side is the power-consumption side. • There are a different number of coils on the primary (NP ) and secondary (NS ) sides. They are wrapped around an iron core. • The primary coils generate an alternating magnetic field which the iron core magnifies and directs through the secondary coils. • The alternating magnetic field induces a current on the secondary side. • The change in current and voltage depend entirely on the relative number of coils on the two sides.

resistors connected in parallel

Two resistors in parallel are like having a thicker wire which offers less resistance. 1 /𝑅𝐸𝑞 = 1 /𝑅1 + 1 /𝑅2 𝑅𝐸𝑞 = 𝑅1𝑅2 /𝑅1 + 𝑅2 capacitance is opposite

electromotive force units

Volts, V

inductive sensors

When the magnetic properties of an AC circuit change, there is a voltage change. • This is how a traffic light trigger works. AC current flows back and forth through the coil and the voltage from coil's self-inductance is monitored. • If a piece of metal enters the alternating magnetic field, currents are induced in it from the detector. • These currents generate their own magnetic field, influencing the magnetic field of the coil. • This results in a drop in the circuit's voltage, which then triggers some action. • This is also how metal detectors work. Metal that passes into the field triggers a change in the circuit's voltage.

electromagnet

a coil that has a soft iron core and that acts as a magnet when an electric current is in the coil

magnetic field lines

always form closed loops may extend to infinity They run through the magnet itself. and run from North to South. • Lines are close together in regions of a strong magnetic field. • Iron filings will align with the magnetic field lines, providing a visualization of them. • Note the similarity of the electric and magnetic dipole fields.

Current units

ampere A

electric field lines

cannot cross each other start on positive charges (or at infinity) and end on negative charges (or infinity). They are directed from positive charge to negative charge. The density of field lines indicates relative strength of the field. Where the lines get closer together, the field is stronger

relationship of Electric Force, electric field & charge

causes action at a distance Like-charges repel, unlike-charges attract. This works in the same way for charge. Charge distorts the space around itself. Other charge reacts to this distortion by experiencing an attractive or repulsive force. point charge: opposite points to charge sphere works like point charge 𝐸 = 𝐹𝐸/q

Higher pressure

compaction

power (supplied & used)

delivery is usually accomplished with AC circuits.

electromotive force

energy per unit electric charge that is imparted by an energy source, such as an electric generator or a battery. Energy is converted from one form to another in the generator or battery as the device does work on the electric charge being transferred within itself. One terminal of the device becomes positively charged, the other becomes negatively charged.

capacitors

have the ability to store and discharge electrical potential energy can be formed from any ungrounded conductor or pair of conductors. • A very common capacitor is made from two parallel plates of metal. it can discharge (releasing the stored energy) in a very short time interval. camera flash

Relationship of Period & frequency

inversely related

sound waves

longitudinal waves, compaction and rarefaction Waves can travel via longitudinal motion (pressure waves) through gases like air, but also through solids and liquids. • The speed of the pressure wave through a material is what we call the speed of sound in that material.

Magnetic poles

north and south

Charge

objects can be _____ by rubbing them against other objects. He labeled an excess of fluid as positive (+), and a scarcity of fluid as negative (-). q, Q is an intrinsic property of matter, independent of its mass. Examples are a glass rod rubbed by silk and a rubber rod rubbed by wool. • The glass rod seems to gain one type of charge, which repelled other glass rods. • The rubber rod seems to gain another type of charge, which repelled other rubber rods. • Rubber rods and glass rods attracted each other.

resistors connected in series

resistance increases Two resistors in series are like having a longer resistor, which increases resistance. 𝑅𝐸𝑞 = 𝑅1 + 𝑅2

Period units

seconds

Doppler Shift

shifts the perceived frequency of waves from a source. For a source traveling toward the observer, it is a higher pitch, and for a source travelling away, it is a lower pitch.

interference

the combination of two or more waves that results in a single wave can be used to improve and modulate the effects of sound waves. continue on as if they never met

AC current

the current moves back and forth (usually quickly). • Rotary electrical generators naturally generate alternating current. • The electrons deliver energy by moving back and forth. • This is similar to the way a hand-saw works. • The teeth deliver energy to the wood by their motion.They cut by moving back and forth. • The symbol in a circuit has a wave-shape that represents the oscillating current. capacitors can support this • Most household power is delivered via AC circuits. • In the US, the oscillation frequency is 60 cycles/s, with a voltage of 120 V. • In Europe, the frequency is 50 cycles/s, with a voltage of 230 V. • An appliance designed for one system will fail to work in the other

DC current

the current runs in only one direction. • This is typical for a circuit with a battery. • A flashlight is a good example of a DC circuit The electrons deliver the energy through the circuit to the filament (resistor). There it is turned into heat and light. • This is similar to the way a chainsaw works. • The teeth deliver energy to the wood by their motion. • They cut by moving in only one direction.

fundamental frequency

the lowest frequency of vibration of a standing wave The simplest possible standing wave is then Node/Anti-node/Node. The simplest standing wave contains just one 'loop', like a jump rope. first harmonic

electric dipole

there are two equal but opposite charges separated by a distance Lines begin on positive charge and end on negative charge -> 𝑝 dipole vector strength is (positive charge)*(separation distance) dipole vector tries to line up with the external field.

magnetic force & the right-hand rule

thumb: direction of force pointer finger: motion or velocity middle finger: magnetic field force is perpendicular to motion and field x is away from observer dot is toward observer

Electric motors

transform electric current into mechanical rotation by running a current through wires near a permanent magnetic field. have a similar design to electric generators. • There is a loop of wire within permanent magnets. • In this case, though, a direct current is run into the loop. • The current through the bottom wire causes a sideways force on the wire. • The opposite current through the top wire causes an opposite force. • These forces generate a torque, which turns the axle of the motor. • A mechanism called a split-ring commutator switches the current's direction just as the loop reaches equilibrium, causing the loop to keep spinning.

electric generators

transform mechanical rotation into alternating current by moving wires through a permanent magnetic field. Picture a conductor moving across magnetic field lines: • Electrons in the wire are a moving charge, so there is a force generated on them along the wire, generating a current. • Now imagine you rotate a wire loop between permanent magnets: • As one wire crosses magnetic field lines and generates a current, the other wire is crossing the opposite way. Together, they push current around the loop. • Current will rise and fall as each wire passes through the field, slows, reverses, passes through again, slows, ... • This naturally generates an alternating current. • More loops generate more current.

Relationship of Wavelength, frequency & speed

v=f*wavelength frequency and wavelength are inversely proportional

voltage units

volts, V

Electromagnets

watch demonstration

power units

watts, W

Current

when a charge moves i, I the direction of motion of positive charge. it is opposite the direction of motion of negative charge, and it is electrons that usually move

resonance in the shower

• Certain frequencies have a wavelength that 'fits' into the chamber, meaning the chamber is an integer number of wavelengths in length. • These frequencies will constructively interfere with each other, causing that pitch to 'resonate' or 'swell'. • That pitch is louder and seems to come from all directions at once, compared to other pitches. • Energy added at the 'right' frequencies constructively adds, or magnifies. • Energy added at the 'wrong' frequencies decays away. • There are many 'right' frequencies because many different length waves can fit in the same chamber

flute

• For a tube with both ends open (like a simple flute), there are anti-nodes at each end. • Air blowing over the mouthpiece sets up vibrational sound waves in the tube. • The mouthpiece is an anti-node. • The fundamental wave is Anti-node/Node/Anti-node. • This is somewhat like the string, whose fundamental is Node/Anti-node/Node. • The tube length is ½ the fundamental wavelength . • Openings along the tube change the location of one of the anti-nodes. • As with other instruments, all the harmonics that fit a particular length will be present at the same time.

Polarizing air cleaner

• Positive charge is placed onto a plate. • Dust motes in the region of the plate become polarized. Electrons move to the side toward the plate, leaving the other side positive. • The negative end is closer to the plate, so the mote is drawn to the plate. It usually sticks there, like a charged balloon. • In both cases, the moving particles draw air along with themselves, causing a current which brings in more dust motes. Thus a fan is not required for these types of air cleaners.

Relationship of Speed of sound & density of material

• Transverse waves can only travel through a solid since the particles move perpendicular to the wave, and so must be attached to the other particles in order to affect them. • The speed of sound in air also depends on the air's temperature and its density. more density means faster

battery

•they contain two separated materials that contain oppositely charged ions. • The separated ions have the potential to exchange charge and equalize the charge between them, but won't until connected in a circuit. • When connected in a circuit, the electrons drift through the ionic material toward the negative terminal of the battery as they seek to pass through the circuit to the positive terminal. The drift at a slow rate so that the battery doesn't discharge all at once. • Moving charges through a potential (voltage) expends energy. So the battery eventually runs out of energy as the charges equalize.

equipotential lines

𝑃𝐸 = 𝑞 ∙ 𝐸 ∙ d the plane of that is the ... spheres centered around the charge. • Equipotential lines never cross and are perpendicular to the field. are surfaces (planes) that have the same electric potential energy for a given charge there. It takes little energy to move along one, but significant energy to move between equipotentials. like a topographic map

parallel

Current splits at the junction before the two components. • Some portion of the current passes through one component. • Another portion passes through the other component at the same time. • Both current streams re-join at the junction after the parallel components, reforming the original current.

speed of sound in materials

The speed of the pressure wave through a material is what we call... • The speed of the pressure wave through a material is what we call the speed of sound in that material. • The speed of sound in air is 343 m/s (at room temp). • In water sound travels at 1500 m/s. • Sound waves travel 6100 m/s in steel.

period

The time for any particle to complete one full cycle. • The variable is usually T, and is measured in seconds. • The period is independent of the size of the initial displacement.

standing waves

a pattern of nodes and anti-nodes of vibration that simulates a wave that is standing still

electric field

a region around a charged particle or object within which a force would be exerted on other charged particles or objects.

transformers

raise voltage & lower current on one end. Then they lower voltage & raise current on the other end. • only work in an AC system.

Lower pressure

rarefaction