# Chapter 23: Electric Current

67 Questions  Settings  Related Topics
• 1.
Electrons are made to flow in a wire when there is
• A.

An imbalance of charges in the wire.

• B.

More potential energy at one end of the wire than the other.

• C.

A potential difference across its ends.

• 2.
An ampere is a unit of electrical
• A.

Pressure.

• B.

Current.

• C.

Resistance.

• D.

All of these

• E.

None of these

• 3.
A wire that carries an electric current
• A.

Is electrically charged.

• B.

May be electrically charged.

• C.

Is never electrically charged.

• 4.
A coulomb of charge that passes through a 6-volt battery is given
• A.

6 joules.

• B.

6 amperes.

• C.

6 ohms.

• D.

6 watts.

• E.

6 newtons.

• 5.
Which statement is correct?
• A.

Charge flows in a closed circuit.

• B.

Voltage flows through an open or a closed circuit.

• C.

Resistance flows through an open circuit.

• D.

Current is the primary cause of voltage.

• 6.
Electrons move in an electrical circuit
• A.

By being bumped by other electrons.

• B.

By colliding with molecules.

• C.

By interacting with an established electric field.

• D.

Because the wires are so thin.

• E.

None of these

• 7.
Stretch a copper wire so that it is thinner and the resistance between its ends
• A.

Decreases.

• B.

Remains unchanged.

• C.

Increases.

• 8.
Heat a copper wire and its electric resistance
• A.

Decreases.

• B.

Remains unchanged.

• C.

Increases.

• 9.
A wire carrying a current is normally charged
• A.

Negatively.

• B.

Positively.

• C.

Not at all.

• 10.
In an ac circuit, the electric field
• A.

Increases via the inverse-square law.

• B.

Changes magnitude and direction with time.

• C.

Is the same everywhere.

• D.

Is non-existent.

• E.

None of these

• 11.
The current through a 10-ohm resistor connected to a 120-V power supply is
• A.

1 A.

• B.

10 A.

• C.

12 A.

• D.

120 A.

• E.

None of these

• 12.
A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor?
• A.

5 V

• B.

10 V

• C.

15 V

• D.

20 V

• E.

More than 20 V

• 13.
When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value?
• A.

2 ohms

• B.

5 ohms

• C.

10 ohms

• D.

20 ohms

• E.

More than 20 ohms

• 14.
The primary source of electrons in an ordinary electrical circuit is
• A.

A dry cell, wet cell or battery.

• B.

The back emf of motors.

• C.

The power station generator.

• D.

The electrical circuit itself.

• E.

None of these

• 15.
The source of electrons lighting an incandescent ac light bulb is
• A.

The power company.

• B.

Electrical outlet.

• C.

Atoms in the light bulb filament.

• D.

The wire leading to the lamp.

• E.

The source voltage.

• 16.
A woman experiences an electrical shock. The electrons making the shock come from the
• A.

Woman's body.

• B.

Ground.

• C.

Power plant.

• D.

Hairdryer.

• E.

Electric field in the air.

• 17.
In a common dc circuit, electrons move at speeds of
• A.

A fraction of a centimeter per second.

• B.

Many centimeters per second.

• C.

The speed of a sound wave.

• D.

The speed of light.

• E.

None of these

• 18.
When a light switch is turned on in a dc circuit, the average speed of electrons in the lamp is
• A.

The speed of sound waves in metal.

• B.

The speed of light.

• C.

1000 cm/s.

• D.

Less than 1 cm/s.

• E.

Dependent on how quickly each electron bumps into the next electron.

• 19.
Alternating current is normally produced by a
• A.

Battery.

• B.

Generator.

• C.

Both of these

• D.

Neither of these

• 20.
The electric power of a lamp that carries 2 A at 120 V is
• A.

1/6 watts.

• B.

2 watts.

• C.

60 watts.

• D.

20 watts.

• E.

240 watts.

• 21.
When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is
• A.

More than the resistance of either lamp.

• B.

Less than the resistance of either lamp.

• C.

None of these

• 22.
When two lamps are connected in series to a battery, the electrical resistance that the battery senses is
• A.

More than the resistance of either lamp.

• B.

Less than the resistance of either lamp.

• C.

None of these

• 23.
On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in
• A.

Parallel.

• B.

Perpendicular.

• C.

Series.

• D.

Haste.

• 24.
Modern automobile headlights are connected in
• A.

Parallel.

• B.

Perpendicular.

• C.

Series.

• D.

None of these

• 25.
There are electrons in the filament of the ac lamp in your bedroom. When you turn on the lamp and it glows, the glowing comes from
• A.

Different electrons; the ones that flow in the circuit to your lamp.

• B.

The same electrons.

• C.

The positive charges that flow in the filament.

• 26.
A 100-Watt lamp glows brighter than a 25-Watt lamp. The electrical resistance of the 100-Watt lamp must be
• A.

Less.

• B.

Greater.

• C.

The same.

• 27.
In an electric circuit, the safety fuse is connected to the circuit in
• A.

Series.

• B.

Parallel.

• C.

Either series or parallel.

• 28.
When two 1-ohm resistors are connected in series, their combined resistance is
• A.

1 ohm, and when connected in parallel, 2 ohms.

• B.

2 ohms, and when in parallel, 1 ohm.

• C.

1/2 ohm, and when in parallel, 2 ohms.

• D.

2 ohms, and when in parallel, 1/2 ohm.

• E.

None of these

• 29.
A circuit breaker often serves the same purpose as a
• A.

Battery

• B.

Fuse.

• C.

Capacitor.

• D.

All of the above choices are correct.

• E.

None of the above choices are correct.

• 30.
A capacitor is useful in
• A.

Boosting the energy output of a circuit.

• B.

Increasing the current in a resistor.

• C.

Smoothing pulsed current.

• D.

Switching dc to ac in a circuit.

• E.

Increasing or decreasing voltage.

• 31.
An electrical diode is useful for
• A.

Storing electrical energy.

• B.

Boosting voltage.

• C.

Limiting current.

• D.

Voltage modification.

• E.

Changing ac to dc.

• 32.
In a 110-volt circuit containing a lamp in series with the voltage source
• A.

110 coulombs of charge flow through the lamp every second.

• B.

110 joules of energy are converted to heat and light in the circuit every second.

• C.

110 joules of energy are given up by each coulomb of charge making up the current in the circuit.

• D.

110 joules of energy are shared among all the coulombs in the circuit at any instant.

• E.

None of the above

• 33.
In a simple circuit containing a bulb, energy is given to the moving charges by
• A.

The bulb.

• B.

The wires.

• C.

A generator.

• D.

None of these

• 34.
A capacitor is used to store
• A.

Both charge and energy.

• B.

Energy.

• C.

Charge.

• D.

Neither charge nor energy.

• 35.
The number of electrons delivered daily to an average American home by an average power utility in the mid 1980s was
• A.

Zero.

• B.

110.

• C.

220.

• D.

Billions of billions.

• E.

None of these

• 36.
Two lamps, one with a thick filament and one with a thin filament, are connected in series. The current is
• A.

Greater in the lamp with the thick filament.

• B.

Greater in the lamp with the thin filament.

• C.

The same in each lamp.

• 37.
Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage is
• A.

Greatest across the lamp with the thick filament.

• B.

Greatest across the lamp with the thin filament.

• C.

The same in both lamps.

• 38.
Two lamps, one with a thick filament and one with a thin filament of the same material, are connected in parallel to a battery. The current is
• A.

Larger in the lamp with the thick filament.

• B.

Larger in the lamp with the thin filament.

• C.

The same in both lamps.

• 39.
Two lamps, one with a thick filament and one with a thin filament of the same material, are connected in series to a battery. The voltage is
• A.

Greater across the lamp with the thick filament.

• B.

Greater across the lamp with the thin filament.

• C.

The same for both lamps.

• 40.
As more lamps are put into a series circuit, the overall current in the power source
• A.

Increases.

• B.

Decreases.

• C.

Stays the same.

• 41.
As more lamps are put into a parallel circuit, the overall current in the power source
• A.

Increases.

• B.

Decreases.

• C.

Stays the same.

• 42.
A circuit is powered with a battery. Charge flows
• A.

Out of the battery and into the circuit.

• B.

From the negative battery terminal to the positive terminal.

• C.

Only after a couple seconds pass.

• D.

Through both the battery and the rest of the circuit.

• E.

None of these

• 43.
When we say an appliance "uses up electricity," we really are saying that
• A.

Current disappears.

• B.

Electric charges are dissipated.

• C.

The main power supply voltage is lowered.

• D.

Electrons are removed from the circuit and placed elsewhere.

• E.

Electron kinetic energy is changed into heat.

• 44.
Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have
• A.

More resistance.

• B.

Less resistance.

• C.

The same resistance.

• 45.
If you plug an electric toaster rated at 110 V into a 220-V outlet, the current in the toaster will be about
• A.

Half what it should be.

• B.

The same as if it were plugged into 110 V.

• C.

More than twice what it should be.

• D.

Twice what it should be.

• 46.
When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is
• A.

0.25 A.

• B.

0.5 A.

• C.

2 A.

• D.

4 A.

• E.

More than 4 A.

• 47.
If 0.8 A of current flow through a light bulb connected to a 120 V outlet, the power consumed is
• A.

12 W.

• B.

15 W.

• C.

60 W.

• D.

96 W.

• E.

120 W.

• 48.
The headlights, radio, and defroster fan in an automobile are connected in
• A.

Series with a switch for each.

• B.

Parallel with a switch for each.

• C.

Series without separate switches.

• D.

Parallel without separate switches.

• 49.
A 4-ohm resistor is connected in parallel with a 6-ohm resistor. This combination produces an equivalent resistance of
• A.

2.4 ohms.

• B.

4 ohms.

• C.

5 ohms.

• D.

5.5 ohms.

• E.

10 ohms.

• 50.
The power dissipated in a 4-ohm resistor carrying 3 A is
• A.

7 W.

• B.

18 W.

• C.

36 W.

• D.

48 W.

• E.

Not enough information to say

• 51.
Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts?
• A.

Touching the light fixture

• B.

Touching the generator

• C.

Touching both are about equally dangerous.

• 52.
A 60-W light bulb and a 100-W light bulb are each rated at 120 V. Which light bulb has a larger resistance?
• A.

The 60-W bulb

• B.

The 100-W bulb

• C.

Both have the same resistance.

• 53.
A 60-W light bulb and a 100-W light bulb are connected in series to a 120 V outlet. Which light bulb has more current in it?
• A.

The 60-W bulb

• B.

The 100-W bulb

• C.

Both have the same current.

• 54.
Compared to the filament thickness of a 60-W light bulb, the filament of a 100-W light bulb will be
• A.

Thinner.

• B.

Thicker.

• C.

The same.

• 55.
Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry
• A.

More current.

• B.

Less current.

• C.

The same current.

• 56.
Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry
• A.

More current.

• B.

Less current.

• C.

The same current.

• 57.
An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the circuit can handle 15 A of current. How many heaters can be safely operated in the circuit?
• A.

2

• B.

3

• C.

4

• D.

5

• E.

More than 5

• 58.
A heater uses 20 A when used in a 110-V line. If electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is
• A.

\$0.22.

• B.

\$0.55.

• C.

\$2.20.

• D.

\$5.50.

• E.

None of these

• 59.
The current through two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is
• A.

22 ohms.

• B.

44 ohms.

• C.

220 ohms.

• D.

440 ohms.

• E.

None of these

• 60.
A power line with a resistance of 2 ohms has a current of 80 A in it. The power dissipated in the line is
• A.

40 W.

• B.

160 W.

• C.

320 W.

• D.

12,800 W.

• E.

None of these

• 61.
What is the resistance of a 120-W incandescent lamp connected to a 120-V power supply?
• A.

1 ohm

• B.

60 ohms

• C.

100 ohms

• D.

144 ohms

• E.

None of these

• 62.
Compared to the amount of electric current in the filament of a lamp, the amount of current in the connecting wire is
• A.

Definitely less.

• B.

Often less.

• C.

Actually more.

• D.

The same.

• E.

Incredibly, all of these

• 63.
Connect a pair of lamps in series and you draw current from the connected battery. Connect the same lamps in parallel and you draw
• A.

The same current.

• B.

More current.

• C.

Less current.

• D.

Sometimes more, sometimes less.

• 64.
Three resistors, 1-ohm, 2-ohm, and 3- ohm are connected in parallel. If they were connected in series instead their equivalent resistance would be
• A.

7 times as great.

• B.

9 times as great.

• C.

11 times as great.

• D.

13 times as great.

• E.

None of the above choices are correct.

• 65.
The ratio of the potential difference across a metallic conductor to the current in the conductor is known as
• A.

Potential drop.

• B.

Conductivity.

• C.

Resistance.

• D.

Electromagnetic force.

• E.

None of the above choices are correct.

• 66.
What condition must exist between two points in a conductor in order to maintain a flow of charge?
• A.

• B.

A high resistance

• C.

A switch connected in series

• D.

All of the above choices are correct.

• E.

None of the above choices are correct.

• 67.
A sphere has a negative charge of 6.4 × 10^(-7) coulomb. The approximate number of electrons that must be removed to make the sphere neutral is
• A.

1.6 × 10^(-8).

• B.

9.8 × 10^3.

• C.

6.4 × 10^26.

• D.

4.0 × 10^12.