Chapter 23: Electric Current
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- 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.
A steady magnetic field
- 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.
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