Physical Science - Exam #3
Why does the north pole of a magnet point to the Earth's magnetic north pole if like poles repel? Check all that apply.
-The geographic North Pole is a magnetic south pole. -The north pole of a magnet is named after "north seeking," so a north pole points north.
An electrostatic charge, commonly called static electricity, can be produced
-by transferring electrons through friction -by transferring electrons direct contact between the objects -by induction which redistributed electrons through a material
When a switch is closed in a DC electrical circuit,
-electrons flow through the conductor at a very slow speed. -the electric field moves through the conductor at nearly the speed of light. -the current flow is proportional to the potential difference.
Electrical charge
-is measure in units of coulombs -of an electron is 1.60 x 10^-19 coulombs -of an electron cannot be divided -of 1 coulomb equals the charge of 6.24 x 10^18 protons
One theory as to the cause of Earth's magnetic field is
. the flowing of liquid iron and nickel within the core as Earth rotates.
In an ideal transformer, the primary voltage is 120 V and the primary current is 2.0A. If the output voltage is 1200 V, the output current will be
0.2 A
The potential difference that is created by doing 1.00 joule of work in moving 1.00 coulomb of charge is defined to be
1.0 volt
What is the current in a 67.9 Ω resistor when the potential difference across it is 120.0 V ?
1.76
An electric current through a wire is 8.28 C every 4.26 s . What is the magnitude of this current?
1.94
A typical air conditioner unit draws a current of 25 A with a voltage of 220V. If the air conditioner "runs" for 240 hours a month, what does it cost to run if the cost of 1 kWh is $0.10.
132$
Which numbered arrow is the refracted ray indicated by?
2
The speed of light is 3.00 x 108 m/s. If the index of refraction of glass is 1.50, The speed of light in glass is
2.00 x 10^8 m/s.
The frequency of a photon of red light that has a wavelength of 680 nm is
2.27 x 10-15 Hz.
Consider an electrical transformer has 10 loops on its primary coil and 20 loops on its secondary coil. What is the current in the secondary if the current is the primary coil is 5.0 A?
2.5 A
Consider an electrical transformer has 10 loops on its primary coil and 20 loops on its secondary coil. What is the voltage in the secondary coil if the primary coil is supplied with 120 V?
240 V
There is a current of 4.30 A through a toaster connected to a 120.0 V circuit. What is the resistance of the toaster?
27.9
If angle A is 60º, what does angle C measure?
30º
If a potential difference of 12.0 V is required to produce a current of 3.0 A in a wire, the resistance of the wire is
4.0 Ohm (Ω)
A ray of orange light has a frequency of 4.9 x 1014 Hz. The corresponding wavelength of this light is
612 nm
Can you name everyday things that make life easier for us because of electromagnets?
A. Electric meters B. Thermostats C. Mechanical switches on VCRs and doorbells D. Electric motors
What is the photoelectric effect?
A. Electrons are emitted when specific materials are exposed to light. B. Energy of a light wave occurs in discrete amounts of energy called quanta. C. Einstein defined the quanta as photons. D. Light is a stream of moving particles called photons
When viewed from a stationary platform, an object moving at speeds approaching the speed of light would, according to the Special Theory of Relativity,
A. be shorter than when it was not moving. B. have an increased mass. C. find that time has slowed down.
Light that interacts with matter can be
A. reflected. B. absorbed. C. transmitted
Which of the following are misconceptions concerning electric current?
AThe electrons move at nearly the speed of light through a wire. B. Electrons are pushed out of the wire as more enter the wire. C. The flow of electrons is like the flow of water in a pipe.
If 1 is the incident ray, what is the angle of reflection?
B
The unit of electric charge is called a(n)
Coulomb
How does an electric generator generate an electric current? The generator
Does work in moving electrons, which creates an electric field.
A common fundamental property of both electrons and protons is
Electric Charge
In an experiment in the late 1800's, J. J. Thomson discovered that all matter contained negatively charged particles. These particles were named after the Greek word for amber. Today these sub-atomic particles are named
Electrons
What causes an electron to move toward one end of a wire when the wire is moved across a magnetic field?
Electrons have magnetic fields that interact with an external magnetic field.
Electrons move from the power plant to homes in an alternating current.
False
If one cuts a current carrying wire, the flow of electricity will spill out into the air.
False
Interference is a property of light most easily explained by the particle model
False
Longer wavelengths are affected more by a prism or water droplets than are the shorter wavelengths.
False
The electrical force is much weaker than the force of gravity.
False
The sky appears blue due to the light reflected from the oceans.
False
A transformer in which the number of turns in the primary coil is greater than the number of turns in the secondary coil
Is called a step down transformer.
Is a kWh a unit of power or a unit of work?
It is a unit of work since W=Pt (from P=W/t)
What are the units of h in the equation E = hf?
Jxs
What property of light do you have to keep in mind while looking at fish in a lake or stream?
Light bends when it hits the air to water interface. The fish that you spotted is not where you think it is.
How is an unmagnetized piece of iron different from the same piece of iron when it is magnetized?
Magnetic domains are randomly oriented in unmagnetized iron, aligned in magnetized iron.
Which of the following is not luminous?
Moon
The frequency of light is
None of the answers is correct
Which of the following properties of light cannot be described by using the wave model of light?
Photoelectric effect
A conductor is a material which has electrons that are free to move. Which of the following is a conductor?
Silver Spoon
The operation of the household circuit breaker depends on what property of an electrical current?
The electrical current produces a magnetic field which opens the circuit breaker.
Why do polarized sunglasses reduce glare (reflected light)?
The reflected light is polarized in the horizontal plane and the glasses are polarized in the vertical plane.
The magnitude of an induced voltage does NOT depend on
The resistance of the wire.
Why is the sky blue?
The shorter wavelengths of blue and violet light are scattered more strongly than red and orange light.
Charge moving through a wire produces a magnetic field around the wire.
True
Glare is light that tends to be polarized predominantly in the horizontal plane.
True
If you double the distance between two charged objects, you reduce the electrical force by a factor of four.
True
The attractive force between two unlike charges has the same strength as the repulsive force between two like charges.
True
The north end of a suspended magnet will point to Earth's magnetic north pole.
True
The range of energies emitted by the Sun is most intense near the yellow-green wavelengths.
True
The slower light through a given substance, the greater the index of refraction.
True
The volt is a measure of the difference in electrical potential energy between two points.
True
Ultraviolet light waves carry more energy than infrared light waves.
True
A lightbulb with a resistance of 14.5 Ω allows a 0.73 A current to flow when connected to a battery.
Voltage: 10.58 Power: 7.72
Electric power is measured in units of
Watts
Which of the following has the highest energy (i.e. highest frequency)?
X-ray
The reason that someone can see a reflection in a mirror is that
a mirror is a smooth surface and light rays reflect from the surface of the mirror are parallel to each other in a definite direction.
What is a magnetic pole?
a side where the magnetic force seems to be concentrated
What is a magnetic pole?
a side where the magnetic force seems to be concentrated
Polarizing sunglasses are useful because they are able to
absorb reflected light, which is polarized.
An electric current is measured in units of
amp
Which of the following unit is actually a measure of a rate?
amp
The rate of flow of electric charge is measured in
amperes
What is it that travels through an electric circuit at near the speed of light?
an electrical field
Max Planck discovered that the blackbody radiation emitted by vibrating molecules
appeared to come in multiples of certain fixed amounts.
Which of the following is an incandescent light source?
candle
Near-sightedness, or myopia, can be corrected with which type lens?
concave
The incident angle of a light ray that travels from water to air and is refracted at 90o is called the
critical angle
The flow of charge is defined as
current
Electric power is
current times voltage
When white light is passed through a prism at the correct angle, the colors of the rainbow are produced. This dispersion of light is due to the fact that
each color of light has its own index of refraction.
When an electric stove element is hot enough, it gives off a dull red glow. When it cools to the point that it no longer glows, it will
emit only longer wavelength energy.
An electric current is a(an)
flow of charge
In 1820, Hans Oersted discovered that electrical currents produce magnetic fields when
he found that a wire carrying a current deflected the needle of a magnetic compass.
A rainbow always appears
in the part of the sky opposite from the Sun.
The majority of the Sun's radiant energy is in the form of
infrared radiation
An electric field
is always present around an electron.
The ratio of the speed of light in a vacuum to the speed of light in a medium
is called the index of refraction
The force between two charged particles
is inversely proportional to the distance between them squared.
The natural magnetic field surrounding Earth
is produced by moving charges in Earth's core.
The north pole of a magnet is so named because
it points to the earth's north magnetic pole.
The Sun appears reddish as it sets because
more of the shorter, bluer wavelengths are scattered away by the dust and haze.
Our eyes are most sensitive to sunlight with a frequency that is
near the yellow-green region of the visible spectrum.
A neutrally charged atom that gains one or more electrons is called a(n)
negative ion
If you were to mechanically rotate the armature in an electric motor
nothing would happen
Electrical resistance is a property of conductors that is measured in units of
ohm
Polarized light vibrates
only in one plane
If you multiply amp Χ ohm, the answers will be in units of
potential
A blue SUV appears blue because it
reflects blue light in the 460 nm to 490 nm range.
A mirage is caused by hot air near the ground
refracting light rays upward.
Ohm's law states
that the current in a circuit increases if the potential difference increases.
The photoelectric effect could not be adequately explained with a wave model of light because
the energy of the ejected electrons did not depend upon the intensity.
The index of refraction for flint glass is 1.5. This means that
the speed of light is slower in this substance than it is in vacuum.
Electric field lines are drawn
to show the direction a test charge would move
Phenomena such as diffraction and interference can be most easily explained in terms of the
wave model of light