## Homework Helpers: Physics

**6 Electric Current and Circuits**

**Chapter 6 Examination**

**Part I—Matching**

Match the following terms to the definitions that follow.

a. current

b. circuit

c. resistance

d. conventional current

e. alternating current

f. direct current

g. electric power

h. Ohm’s Law

i. resistivity

_______1.__ Electric current that periodically reverses directions.

_______2.__ Visualization of current flowing out of the positive terminal into the negative terminal.

_______3.__ An arrangement of components that provides one or more pathways for electric current to flow.

_______4.__ The rate at which electrical energy is transformed.

_______5.__ The opposition to the flow of electric current.

**Part II—Multiple Choice**

For each of the following questions choose the best answer.

__6.__ What units are used to measure resistance?

a) amps

b) volts

c) ohms

d) watts

__7.__ What units are used to measure power?

a) amps

b) volts

c) ohms

d) watts

__8.__ Which of the following quantities are measured in units called *volts*?

a) current

b) potential difference

c) potential energy

d) work

__9.__ A wire carries a current of 3.0 A. How much charge passes by a point in 90.0 seconds?

a) 270 C

b) 30 C

c) 87 C

d) 93 C

__10.__ Calculate the current through a 3.0Ω resistor with a voltage of 9.0 V across it.

a) 0.33 A

b) 27 A

c) 3.0 A

d) 6.0 A

__11.__ Three resistors with resistances of 2.0Ω, 4.0Ω, and 7.0Ω, respectively, are connected in a series circuit. Find the equivalent resistance.

a) 1.1Ω

b) 13.0Ω

c) 56.0Ω

d) 93Ω

__12.__ Three resistors with resistances of 1.0Ω, 7.0Ω, and 9.0Ω, respectively, are connected in a parallel circuit to a 9.0 V battery. Find the potential difference across the 9.0Ω resistor.

a) 1.0 V

b) 1.5 V

c) 9.0 V

d) 12.0 V

__13.__ Find the power dissipated by a 7.0Ω resistor with a current of 2.0 A through it.

a) 5.0 W

b) 9.0 W

c) 14 W

d) 28 W

__14.__ What is the power dissipated by a 5.0Ω resistor with a potential difference of 9.0 V across it?

a) 4.0 W

b) 5.0 W

d) 14 W

d) 16 W

**Part III—Calculations**

Perform each of the following calculations.

__15.__ 120 C of charge pass a point in a wire every minute. What is the current in the wire?

__16.__ A bulb has a potential difference of 6.0 V across it and a current of 1.0 A through it. Calculate its resistance.

__17.__ Calculate the current through a 9.0Ω resistor that operates at 30.0 W.

__18.__ What is the power developed in a 6.0Ω resistor with a potential of 1.5 V across it?

__19.__ Three resistors with resistances of 5.0Ω, 9.0Ω, and 12.0Ω, respectively, are connected in a series circuit with a 6.0 V battery. Find the potential difference across the 5.0Ω resistor.

__20.__ My electric fan draws 0.55 A of current with a potential difference of 120 V across it. If I pay $0.17/kW-h, how much will it cost me to operate this fan for 3.00 hours?