Chapter 23
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Chapter 23 . Electric Current. The flow of charge in an electric circuit is much. like the flow of water in a system of pipes. different than water flow in pipes. like an electric valve. like an electric pump. The flow of charge in an electric circuit is much.

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Chapter 23

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Chapter 23

Electric Current


The flow of charge in an electric circuit is much

  • like the flow of water in a system of pipes.

  • different than water flow in pipes.

  • like an electric valve.

  • like an electric pump.


The flow of charge in an electric circuit is much

  • like the flow of water in a system of pipes.

  • different than water flow in pipes.

  • like an electric valve.

  • like an electric pump.


Electric charge will flow in an electric circuit when

  • electrical resistance is low enough.

  • a potential difference exists.

  • the circuit is grounded.

  • electrical devices in the circuit are not defective.


Electric charge will flow in an electric circuit when

  • electrical resistance is low enough.

  • a potential difference exists.

  • the circuit is grounded.

  • electrical devices in the circuit are not defective.


The electric current in a copper wire is normally composed of

  • electrons.

  • protons.

  • ions.

  • All or any of these.


The electric current in a copper wire is normally composed of

  • electrons.

  • protons.

  • ions.

  • All or any of these.

Explanation: Although current can consist of protons and ions, in a copper wire current consists of electrons appropriately called conduction electrons.


Which statement is correct?

  • Voltage flows in a circuit.

  • Charge flows in a circuit.

  • A battery is the source of electrons in a circuit.

  • All are correct.


Which statement is correct?

  • Voltage flows in a circuit.

  • Charge flows in a circuit.

  • A battery is the source of electrons in a circuit.

  • All are correct.

Explanation: Voltage causes the flow of electrons, and doesn’t flow. Charges flow. A battery is a source of energy, not electrons.


Apply heat to a copper wire and the resistance of the wire

  • decreases.

  • remains unchanged.

  • increases.

  • vanishes with enough heat.


Apply heat to a copper wire and the resistance of the wire

  • decreases.

  • remains unchanged.

  • increases.

  • vanishes with enough heat.


The amount of current in a circuit depends on the

  • voltage across the circuit.

  • electrical resistance of the circuit.

  • Both of these.

  • None of these.


The amount of current in a circuit depends on the

  • voltage across the circuit.

  • electrical resistance of the circuit.

  • Both of these.

  • None of these.


When you double the voltage in a simple electric circuit, you double the

  • current.

  • resistance.

  • Both of these.

  • None of these.


When you double the voltage in a simple electric circuit, you double the

  • current.

  • resistance.

  • Both of these.

  • None of these.

Explanation: This is straight-forward Ohm’s law. Current = voltage/resistance.


When 110 volts are impressed across a 22-ohm resistor, the current in the resistor is

  • 5 A.

  • 10 A.

  • 132 A.

  • 2420 A.


When 110 volts are impressed across a 22-ohm resistor, the current in the resistor is

  • 5 A.

  • 10 A.

  • 132 A.

  • 2420 A.


To receive an electric shock there must be

  • current in one direction.

  • moisture in the electrical device being used.

  • a difference in potential across part or all of the body.

  • high voltage and low body resistance.


To receive an electric shock there must be

  • current in one direction.

  • moisture in the electrical device being used.

  • a difference in potential across part or all of the body.

  • high voltage and low body resistance.


The difference between dc and ac in electrical circuits is that in dcthe electrons

  • flow steadily in one direction only.

  • flow in one direction only.

  • steadily flow to and fro.

  • flow to and fro.


The difference between dc and ac in electrical circuits is that in dc the electrons

  • flow steadily in one direction only.

  • flow in one direction only.

  • steadily flow to and fro.

  • flow to and fro.


Which device is used to convert ac to a fairly steady dc?

  • Diode

  • Capacitor

  • Both of these.

  • None of these.


Which device is used to convert ac to a fairly steady dc?

  • Diode

  • Capacitor

  • Both of these.

  • None of these.

Explanation: Although a diode will convert ac to dc, the additional use of a capacitor produces steadiness (as Figure 23.11 in the text shows).


What travels at about the speed of light in an electric circuit?

  • Electric charges

  • Electric current

  • Electric field

  • All of these.


What travels at about the speed of light in an electric circuit?

  • Electric charges

  • Electric current

  • Electric field

  • All of these.

Explanation: The electric field in a circuit travels at nearly the speed of light, not the electrons nor the current.


When you buy a water pipe in a hardware store, the water isn’t included. When you buy copper wire, electrons

  • must be supplied by you, just as water must be supplied for a water pipe.

  • are already in the wire.

  • may fall out, which is why wires are insulated.

  • None of these.


When you buy a water pipe in a hardware store, the water isn’t included. When you buy copper wire, electrons

  • must be supplied by you, just as water must be supplied for a water pipe.

  • are already in the wire.

  • may fall out, which is why wires are insulated.

  • None of these.


The drift speed of electrons that make up current in a circuit is

  • near the speed of light.

  • near the speed of sound.

  • about a snail’s pace.

  • imaginary.


The drift speed of electrons that make up current in a circuit is

  • near the speed of light.

  • near the speed of sound.

  • about a snail’s pace.

  • imaginary.


If you double both the current and the voltage in a circuit, the power

  • remains unchanged if resistance remains constant.

  • halves.

  • doubles.

  • quadruples.


If you double both the current and the voltage in a circuit, the power

  • remains unchanged if resistance remains constant.

  • halves.

  • doubles.

  • quadruples.

Explanation: Electric power = current  voltage. Doubling both current and voltage corresponds to 4 times as much power.


A lamp with a current of 10 A connected to 120 volts consumes a power of

  • 10 W.

  • 12 W.

  • 120 W

  • 1200 W.


A lamp with a current of 10 A connected to 120 volts consumes a power of

  • 10 W.

  • 12 W.

  • 120 W

  • 1200 W.


Which of these lamps is the longer lasting in a common circuit?

  • Incandescent lamp

  • Compact fluorescent lamp

  • Light-emitting diode

  • All about the same.


Which of these lamps is the longer lasting in a common circuit?

  • Incandescent lamp

  • Compact fluorescent lamp

  • Light-emitting diode

  • All about the same.

Comment: More about LEDs in Chapter 30.


In a simple circuit consisting of a single lamp and a single battery, when current in the lamp is 2 amperes, the current in the battery is

  • half, 1 A.

  • 2 A.

  • dependent on internal battery resistance.

  • Not enough information to say.


In a simple circuit consisting of a single lamp and a single battery, when current in the lamp is 2 amperes, the current in the battery is

  • half, 1 A.

  • 2 A.

  • dependent on internal battery resistance.

  • Not enough information to say.

Comment: It is important to know that the current in the devices in series is also the current in the battery. Current will depend on battery resistance, but if there’s 2 A in the circuit, there’s 2 A in the battery!


In a circuit with two lamps in parallel, if the current in one lamp is 2 amperes, the current in the battery is

  • half, 1 A.

  • 2 A.

  • more than 2 A.

  • Not enough information to say.


In a circuit with two lamps in parallel, if the current in one lamp is 2 amperes, the current in the battery is

  • half, 1 A.

  • 2 A.

  • more than 2 A.

  • Not enough information to say.

Explanation: Current in the battery will be the sum of currents in the two branches.


One way to prevent overloading in your home circuit is to

  • operate fewer devices at the same time.

  • change the wiring from parallel to series for troublesome devices.

  • find a way to bypass the fuse or circuit breaker.

  • All of these.


One way to prevent overloading in your home circuit is to

  • operate fewer devices at the same time.

  • change the wiring from parallel to series for troublesome devices.

  • find a way to bypass the fuse or circuit breaker.

  • All of these.


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