SCNC 102- Exam 3

Electricity and Light

1. Electrostatic charge results from

a. transfer or redistribution of electrons.

b. gain or loss of protons.

c. separation of charge from electrons and protons.

d. failure to keep the object clean of dust.

transfer or redistribution of electrons.

2. The unit of electric charge is the

a. volt.

b. amp.

c. coulomb.

d. watt.

coulomb.

3. An electric field describes the condition of space around

a. a charged particle.

b. a magnetic pole.

c. a mass.

d. all of the above.

a charged particle

4. A material that has electrons that are free to move throughout the material is a (an)

a. electrical conductor.

b. electrical insulator.

c. thermal insulator.

d. thermal nonconductor.

electrical conductor

5. An example of an electrical insulator is

a. graphite.

b. glass.

c. aluminum.

d. tungsten.

glass.

6. The electrical potential difference between two points in a circuit is measured in units of

a. volt.

b. amp.

c. coulomb.

d. watt.

volt.

7. The rate at which an electric current flows through a circuit is measured in units of

a. volt.

b. amp.

c. coulomb.

d. watt.

amp.

8. The law that predicts the behavior of electrostatic forces acting through space is

a. the law of universal gravitation.

b. Watt’s law.

c. Coulomb’s law.

d. Ohm’s law.

Coulomb’s law

9. What type of electric current is produced by fuel cells and solar cells?

a. ac

b. dc

c. 60 Hz

d. 120 Hz

dc

10. The electrical resistance of a conductor is measured in units of

a. volt.

b. amp.

c. ohm.

d. watt.

ohm.

11. According to Ohm’s law, what must be greater to maintain the same current in a conductor with more resistance?

a. Voltage

b. Current

c. Temperature

d. Cross-sectional area

Voltage

12. A kilowatt-hour is a unit of

a. power.

b. work.

c. current.

d. potential difference.

work.

13. If you multiply volts by amps, the answer will be in units of

a. power.

b. work.

c. current.

d. potential difference.

power.

14. Units of joules per second are a measure called a (an)

a. volt.

b. amp.

c. ohm.

d. watt.

watt.

15. A lodestone is a natural magnet that attracts

a. iron.

b. cobalt.

c. nickel.

d. all of the above.

all of the above

16. The north pole of a suspended or floating bar magnet currently points directly toward Earth’s

a. north magnetic pole.

b. south magnetic pole.

c. north geographic pole.

d. south geographic pole.

north magnetic pole.

17. A current-carrying wire always has

a. a magnetic field with closed concentric field lines around the length of the wire.

b. a magnetic field with field lines parallel to the length of the wire.

c. an electric field but no magnetic field around the wire.

d. nothing in the space around the wire.

a magnetic field with closed concentric field lines around the length of the wire.

18. Magnetism is produced by

a. an excess of north monopoles.

b. an excess of south monopoles.

c. moving charges.

d. separation of positive and negative charges.

moving charges.

19. Earth’s magnetic field

a. has undergone many reversals in polarity.

b. has always been as it is now.

c. is created beneath Earth’s north geographic pole.

d. is created beneath Earth’s south geographic pole.

has undergone many reversals in polarity.

20. The strength of a magnetic field around a current-carrying wire varies directly with the

a. amperage of the current.

b. voltage of the current.

c. resistance of the wire.

d. temperature of the wire.

amperage of the current.

21. Reverse the direction of a current in a wire, and the magnetic field around the wire will

a. have an inverse magnitude of strength.

b. have a reversed north pole direction.

c. become a conventional current.

d. remain unchanged.

have a reversed north pole direction.

22. The operation of which of the following depends on the interaction between two magnetic fields?

a. Car stereo speakers

b. Telephone

c. Relay circuit

d. All of the above

All of the above

23. An electric meter measures the

a. actual number of charges moving through a conductor.

b. current in packets of coulombs.

c. strength of a magnetic field.

d. difference in potential between two points in a conductor.

strength of a magnetic field.

24. When a loop of wire cuts across magnetic field lines or when magnetic field lines move across a loop of wire,

a. electrons are pushed toward one end of the loop.

b. an electrostatic charge is formed.

c. the wire becomes a permanent magnet.

d. a magnetic domain is created.

electrons are pushed toward one end of the loop.

25. A step-up transformer steps up the

a. voltage.

b. current.

c. power.

d. energy.

voltage.

26. Electromagnetic induction occurs when a coil of wire cuts across magnetic field lines. Which one of the following increases the voltage produced?

a. Fewer wire loops in the coil

b. Increased strength of the magnetic field

c. Slower speed of the moving coil of wire

d. Decreased strength of the magnetic field

Increased strength of the magnetic field

27. Electric power companies step up the voltage of generated power for transmission across the country because higher voltage

a. means more power is transmitted.

b. reduces the current, which increases the resistance.

c. means less power is transmitted.

d. reduces the current, which lowers the energy lost to resistance.

reduces the current, which lowers the energy lost to resistance.

28. A solar cell

a. produces electricity directly.

b. requires chemical reactions.

c. has a very short lifetime.

d. uses small moving parts.

produces electricity directly.

29. Which of the following is most likely to acquire an electrostatic charge?

a. Electrical conductor

b. Electrical nonconductor

c. Both are equally likely

d. None of the above is correct

Electrical nonconductor

30. Which of the following units are measures of rates?

a. Amp and volt

b. Coulomb and joule

c. Volt and watt

d. Amp and watt

Amp and watt

31. You are using which description of a current if you consider a current to be positive charges that flow from the positive to the negative terminal of a battery?

a. Electron current

b. Conventional current

c. Proton current

d. Alternating current

Conventional current

32. In an electric current, the electrons are moving

a. at a very slow rate.

b. at the speed of light.

c. faster than the speed of light.

d. at a speed described as supersonic.

at a very slow rate.

33. In which of the following currents is there no electron movement from one end of a conducting wire to the other end?

a. Electron current

b. Direct current

c. Alternating current

d. None of the above

Alternating current

34. If you multiply amps by volts, the answer will be in units of

a. resistance.

b. work.

c. current.

d. power.

power.

35. A permanent magnet has magnetic properties because

a. the magnetic fields of its electrons are balanced.

b. of an accumulation of monopoles in the ends.

c. the magnetic domains are aligned.

d. all of the above.

the magnetic domains are aligned.

36. A current-carrying wire has a magnetic field around it because

a. a moving charge produces a magnetic field of its own.

b. the current aligns the magnetic domains in the metal of the wire.

c. the metal was magnetic before the current was established, and the current enhanced the magnetic effect.

d. None of the above is correct.

a moving charge produces a magnetic field of its own.

37. When an object acquires a negative charge, it actually

a. gains mass.

b. loses mass.

c. has a constant mass.

d. The answer is unknown.

gains mass.

38. A positive and a negative charge are initially 2 cm apart. What happens to the force on each as they are moved closer and closer together? The force

a. increases while moving.

b. decreases while moving.

c. remains constant.

d. The answer is unknown.

increases while moving.

39. To be operational, a complete electric circuit must contain a source of energy, a device that does work, and

a. a magnetic field.

b. a conductor from the source to the working device and another conductor back to the source.

c. connecting wires from the source to the working device.

d. a magnetic field and a switch.

a conductor from the source to the working device and another conductor back to the source.

40. Which variable is inversely proportional to the resistance?

a. Length of conductor

b. Cross-sectional area of conductor

c. Temperature of conductor

d. Conductor material

Cross-sectional area of conductor

41. Which of the following is not considered to have strong magnetic properties?

a. Iron

b. Nickel

c. Silver

d. Cobalt

Silver

42. A piece of iron can be magnetized or unmagnetized. This is explained by the idea that

a. electrons in iron atoms are spinning and have magnetic fields around them.

b. atoms of iron are grouped into tiny magnetic domains that may orient themselves in a particular direction or in a random direction.

c. unmagnetized iron atoms can be magnetized by an external magnetic field.

d. the north and south poles of iron can be segregated by the application of an external magnetic field.

atoms of iron are grouped into tiny magnetic domains that may orient themselves in a particular direction or in a random direction.

43. Earth’s magnetic field is believed to originate

a. by a separation of north and south monopoles due to currents within Earth.

b. with electric currents that are somehow generated in Earth’s core.

c. from a giant iron and cobalt bar magnet inside Earth.

d. from processes that are not understood.

with electric currents that are somehow generated in Earth’s core.

44. Electromagnetic induction takes place because

a. an electric current is measured by the rate of movement of charges.

b. the potential is determined by how much work is done.

c. electrons have their own magnetic field, which interacts with an externally applied magnetic field.

d. copper wire is magnetic, which induces magnetism.

electrons have their own magnetic field, which interacts with an externally applied magnetic field.

45. The current in the secondary coil of a transformer is produced by a

a. varying magnetic field.

b. varying electric field.

c. constant magnetic field.

d. constant electric field.

varying magnetic field.

46. An electromagnet uses

a. a magnetic field to produce an electric current.

b. an electric current to produce a magnetic field.

c. a magnetic current to produce an electric field.

d. an electric field to produce a magnetic current.

an electric current to produce a magnetic field.

47. A transformer

a. changes the voltage of a direct current.

b. changes the power of a direct current.

c. changes the voltage of an alternating current.

d. changes the amperage of an alternating current.

changes the voltage of an alternating current.

48. A parallel circuit has

a. wires that are lined up side by side.

b. the same current flowing through one resistance after another.

c. separate pathways for the current to flow through.

d. none of the above.

separate pathways for the current to flow through.

49. In which type of circuit would you expect a reduction of the available voltage as more and more resistances are added to the circuit?

a. Series circuit

b. Parallel circuit

c. Open circuit

d. None of the above

Series circuit

50. In which type of circuit would you expect the same voltage with an increased current as more and more resistances are added to the circuit?

a. Series circuit

b. Parallel circuit

c. Open circuit

d. None of the above

Parallel circuit

Electrostatic charge

the electric charge is confined to an object and is not moving

Coulomb

The quantity of such a charge (q) is measured in a unit called

Electrical conductors

Materials like the metal of a doorknob are good _______ because they have electrons that are free to move throughout the metal

Fundamental charge

smallest common charge known

Coulomb’s law

Attracts opposite signs and repelling like signs.

Electric field

force field is produced by an electrical charge

Force field

a vector field in physics defining non-contact forces (e.g., gravity, electromagnetism) acting on particles at specific locations

Volt

measure of electric potential difference between two points

Electric circuit

contains some device, such as a battery or electric generator, that acts as a source of energy for the devices in the circuit

Electric current

flow of charge

Amp

unit of electrical current. one coulomb of charge per second, short for ampere

Ampere

unit of electrical current. one coulomb of charge per second

Drift velocity

average velocity at which free electrons in a conductor move toward the positive terminal

Alternatic current

moves the electrons alternately one way, then the other way

Direct current

circuit like the one described with your car battery has a current that always moves in one direction

Electrical resistance

Materials have a property of opposing or reducing a current

Ohm

unit of resistance

Ohm’s law

Another way to show the relationship between the voltage, current, and resistance is

Watt

joule/second is a unit of power

Magnetic poles

Every magnet has two ends, about which the force of attraction seems to be concentrated.

Magnetic field

can be represented by magnetic field lines, in a manner very similar to the way that electric fields are represented by drawings of electric field lines

Magnetic domain

In materials that exhibit magnetic properties, atoms are grouped into tiny regions called

Electromagnet

Magnet can be turned on or off by turning the current on or off

Electromagnetic induction

The voltage is called an induced voltage, and the resulting current in the wire is called an induced current. The overall interaction is called

Electric generator

an axle with many wire loops that rotates in a magnetic field. The axle is turned by some form of mechanical energy, such as a water turbine or a steam turbine, which uses steam generated from fossil fuels or nuclear energy. As the coil rotates in a magnetic field, a current is induced in the coil

Transformer

a device that steps up or steps down the ac voltage

Parallel circuit

Cells with all positive terminals connected and all negative terminals connected

Series circuit

A _____ circuit has the negative terminal of one cell connected to the positive terminal of another cell

Short circuit

In addition to overloads, fuses and circuit breakers are “blown” or “tripped” by a ______ circuit, a new path of lesser electrical resistance.

1. Which of the following is luminous?

a. Moon

b. Mars

c. Sun

d. All of the above

Sun

2. A source of light given off as a result of high temperatures is said to be

a. luminous.

b. blackbody radiation.

c. incandescent.

d. electromagnetic radiation.

incandescent

3. An idealized material that absorbs and perfectly emits electromagnetic radiation is a (an)

a. star.

b. blackbody.

c. electromagnetic wave.

d. photon.

blackbody

4. Electromagnetic radiation is given off from matter at any temperature. This radiation is called

a. luminous.

b. blackbody radiation.

c. incandescent.

d. bioluminous radiation.

blackbody radiation

5. Light interacts with matter by which process?

a. Absorption

b. Reflection

c. Transmission

d. All of the above

All of the above

6. Materials that do not allow the transmission of any light are called

a. transparent.

b. colored.

c. opaque.

d. blackbody.

opaque

7. Light is said to travel in straight-line paths, as light rays, until it interacts with matter. A line representing the original ray before it interacts with matter is called a (an)

a. incoming light ray.

b. incident ray.

c. reflected light ray.

d. normal ray.

incident ray

8. The image you see in a mirror is

a. a real image.

b. a virtual image.

c. not really an image.

a virtual image

9. Refraction of light happens when light undergoes

a. reflection from a surface.

b. a change of speed between two transparent materials.

c. movement through a critical angle.

d. a 90° angle of incidence.

a change of speed between two transparent materials

10. The ratio of the speed of light in a vacuum to the speed of light in a transparent material is called the

a. index of deflection.

b. index of reflection.

c. index of refraction.

d. index of diffusion.

index of refraction

11. The part of the electromagnetic spectrum that our eyes can detect is

a. ultraviolet.

b. infrared.

c. visible.

d. all of the above

visible

12. The component colors of sunlight were first studied by

a. Joule.

b. Galileo.

c. Newton.

d. Watt.

Newton

13. The color order of longer-wavelength to smaller-wavelength waves in the visible region is

a. red, orange, yellow, green, blue, violet.

b. red, violet, blue, yellow, green.

c. violet, blue, green, yellow, orange, red.

d. violet, red, blue, green, yellow, orange.

red, orange, yellow, green, blue, violet.

14. The separation of white light into its component colors is

a. reflection.

b. refraction.

c. dispersion.

d. transmission.

dispersion.

15. Polarization of light is best explained by considering light to be

a. vibrating waves in one plane.

b. moving particles in one plane.

c. none of the above.

vibrating waves in one plane.

16. Light in one plane is transmitted and light in all other planes is absorbed. This is

a. selective absorption.

b. polarized absorption.

c. reflection.

d. scattering.

selective absorption.

17. The photoelectric effect is best explained by considering light to be

a. vibrating waves.

b. moving particles.

c. none of the above.

moving particles.

18. The concept that vibrating molecules emit light in discrete amounts of energy, called quanta, was proposed by

a. Newton.

b. Fresnel.

c. Planck.

d. Maxwell.

Planck.

19. The photoelectric effect was explained, using Planck’s work, by

a. Planck.

b. Einstein.

c. Maxwell.

d. Young.

Einstein.

20. Today, light is considered to be packets of energy with a frequency related to its energy. These packets are called

a. gravitons.

b. gluons.

c. photons.

d. quarks.

photons.

21. Fiber optics transmits information using

a. sound.

b. computers.

c. light.

d. all of the above.

light.