Current and Resistance

A 60-W light bulb is in a socket supplied with 120 V. What is the current in the bulb? A. 0.50 A B. 2.0 A C. 60 A D. 7 200 A E. 10 000 A

A

The unit of electric resistance, the ohm, is equivalent to which of the following? A. V/A B. V⋅m C. A/s D. A/m E. A/V

A

A light bulb with a tungsten filament is attached to a source of variable voltage. As the voltage is increased on the bulb, A. the bulb's resistance decreases. B. the bulb's resistance increases. C. the current in the bulb decreases. D. the power dissipated remains constant. E. the bulb's resistance remains constant.

B

If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element? A. 2 000 V B. 125 V C. 250 V D. 0.008 V E. 0.125 V

B

If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire? A. It stays the same. B. It triples. C. It decreases by a factor of three. D. It increases by a factor of nine. E. It decreases by a factor of nine.

B

The unit of electric current, the ampere, is equivalent to which of the following? A. V⋅ohm B. V/ ohm C. ohm⋅m D. V/s E.ohm /V

B

When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field? A. must be zero B. must be parallel to current flow C. must be anti-parallel (opposite direction) to current flow D. must be perpendicular to current flow E. None of the above choices is valid.

B

You measure a 25.0-V potential difference across a 5.00- resistor. What is the current flowing through it? A. 125 A B. 5.00 A C. 4.00 A D. 1.00 A E. 0.125 A

B

A light bulb has resistance of 240 when operating at 120 V. Find the current in the light bulb. A. 2.0 A B. 1.0 A C. 0.50 A D. 0.20 A E. 0.30 A

C

A wire carries a steady current of 0.1 A over a period of 20 s. What total charge passes through the wire in this time interval? A. 200 C B. 20 C C. 2 C D. 0.005 C E. 0.002 C

C

Materials having resistance changes as voltage or current varies are called: A. ohmic. B. inohmic. C. nonohmic D. deohmic. E. ohmless.

C

The current in an electron beam in a cathode-ray tube is measured to be 70 μA. How many electrons hit the screen in 5.0 s? (e = 1.6 × 10-19 C) A. 2.2 × 1011 electrons B. 8.8 × 1013 electrons C. 2.2 × 1015 electrons D. 8.8 × 1018 electrons E. 2.2 × 1020 electrons

C

The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following? A. V/s B. A⋅ ohm C. V⋅A D. V/ohm E. A/V

C

Which is not a force? A. gravity D. friction B. electrical force E. sliding resistance force C. voltage

C

The quantity volt is equivalent to which of the following? A. J⋅m B. J⋅C C. C/ D. J/C E. C/J

D

Which is a unit of power? A. kWh B. W/s C. A⋅ D. J/s E. J/kg

D

If a certain resistor obeys Ohm's law, its resistance will change: A. as the voltage across the resistor changes. B. as the current through the resistor changes. C. as the energy given off by the electrons in their collisions changes. D. as the electric field inside the resistor changes. E. none of the above, since resistance is a constant for the given resistor.

E

The size of the electric current in an electrical conductor is a function of which of the following? A. velocity of charge carriers B. conductor cross sectional area C. density of charge carriers D. conductor length E. All of the above choices are valid.

E