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# Chapter 23 PowerPoint PPT Presentation

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.

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.

• 5 A.

• 10 A.

• 132 A.

• 2420 A.

• 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.

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

• remains unchanged if resistance remains constant.

• halves.

• doubles.

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

• 10 W.

• 12 W.

• 120 W

• 1200 W.

• 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.