# 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.

C. A potential difference across its ends.
Explanation
When there is a potential difference across the ends of a wire, it creates an electric field that exerts a force on the electrons in the wire. This force causes the electrons to move and flow in the wire, creating an electric current. Therefore, the presence of a potential difference across the ends of the wire is what causes electrons to flow, rather than an imbalance of charges or more potential energy at one end.

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• 2.

### An ampere is a unit of electrical

• A.

Pressure.

• B.

Current.

• C.

Resistance.

• D.

All of these

• E.

None of these

B. Current.
Explanation
An ampere is a unit of electrical current. It measures the rate at which electric charge flows in a circuit. It is commonly used to quantify the amount of current flowing through a conductor. The other options, such as electrical pressure and resistance, are not correct because they do not accurately describe what an ampere measures. Therefore, the correct answer is current.

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• 3.

### A wire that carries an electric current

• A.

Is electrically charged.

• B.

May be electrically charged.

• C.

Is never electrically charged.

B. May be electrically charged.
Explanation
A wire that carries an electric current may be electrically charged because the flow of electric charges through the wire creates an electric field around it. This electric field can cause the wire to become charged, depending on the conditions and materials involved. Therefore, it is possible for a wire carrying an electric current to be electrically charged.

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• 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.

A. 6 joules.
Explanation
When a coulomb of charge passes through a 6-volt battery, it gains 6 joules of energy. This is because the energy gained by a charge is equal to the product of the voltage and the charge. In this case, the voltage is 6 volts, and the charge is 1 coulomb. Therefore, the energy gained is 6 joules.

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• 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.

A. Charge flows in a closed circuit.
Explanation
The correct answer is "Charge flows in a closed circuit." This statement is correct because in order for electric current to flow, there must be a complete path for the charges to travel, which is provided by a closed circuit. Charge is the fundamental property of matter that carries electric current, and it moves from a higher potential to a lower potential within the circuit. Therefore, charge flowing in a closed circuit is an essential requirement for the flow of electric current.

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• 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

C. By interacting with an established electric field.
Explanation
Electrons move in an electrical circuit by interacting with an established electric field. When a voltage is applied to a circuit, an electric field is created, which exerts a force on the electrons. This force causes the electrons to move through the circuit, from the negative terminal to the positive terminal. The electrons do not move by being bumped by other electrons or by colliding with molecules, as these interactions do not provide a consistent and directed motion. The thickness of the wires does not play a significant role in the movement of electrons in a circuit.

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• 7.

### Stretch a copper wire so that it is thinner and the resistance between its ends

• A.

Decreases.

• B.

Remains unchanged.

• C.

Increases.

C. Increases.
Explanation
When a copper wire is stretched and made thinner, its cross-sectional area decreases. Resistance is directly proportional to the length of the wire and inversely proportional to its cross-sectional area. Therefore, when the cross-sectional area decreases, the resistance increases.

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• 8.

### Heat a copper wire and its electric resistance

• A.

Decreases.

• B.

Remains unchanged.

• C.

Increases.

C. Increases.
Explanation
When a copper wire is heated, its electric resistance increases. This is because as the temperature of the wire increases, the atoms in the wire vibrate more vigorously, which leads to more collisions between the electrons and the atoms. These collisions impede the flow of electrons, causing an increase in resistance. Therefore, heating a copper wire results in an increase in its electric resistance.

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• 9.

### A wire carrying a current is normally charged

• A.

Negatively.

• B.

Positively.

• C.

Not at all.

C. Not at all.
Explanation
When a wire carries a current, it does not become charged. The movement of electrons in the wire creates the flow of current, but it does not result in a net accumulation of charge on the wire. Therefore, the wire is not charged positively or negatively.

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• 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

B. Changes magnitude and direction with time.
Explanation
In an AC (alternating current) circuit, the electric field changes magnitude and direction with time. This is because AC circuits have a constantly changing voltage and current, which causes the electric field to vary in strength and direction. As the current alternates between positive and negative values, the electric field also changes accordingly. This is in contrast to a DC (direct current) circuit, where the electric field remains constant in magnitude and direction.

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• 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

C. 12 A.
Explanation
The current through a resistor can be calculated using Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the voltage is given as 120 V and the resistance is 10 ohms. Therefore, the current is calculated as 120 V / 10 ohms = 12 A.

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• 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

E. More than 20 V
Explanation
According to Ohm's Law, the voltage across a resistor is equal to the current flowing through it multiplied by the resistance. In this case, the current is 5 A and the resistance is 10 ohms. Therefore, the voltage across the resistor is 5 A * 10 ohms = 50 V. Since 50 V is more than 20 V, the answer is "more than 20 V".

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• 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

B. 5 ohms
Explanation
The current in a resistor is determined by Ohm's Law, which states that the current (I) flowing through a resistor is equal to the voltage (V) across the resistor divided by the resistance (R) of the resistor. In this case, we are given that the current is 2 A and the voltage is 10 V. By rearranging Ohm's Law to solve for resistance, we can calculate the resistor's value. The formula is R = V/I, so the resistor's value is 10 V / 2 A = 5 ohms.

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• 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

D. The electrical circuit itself.
Explanation
The primary source of electrons in an ordinary electrical circuit is the electrical circuit itself. When a circuit is closed, electrons flow from the negative terminal of the power source (such as a battery) through the circuit to the positive terminal. The power source provides the initial push to start the flow of electrons, but once the circuit is established, the electrons continue to move within the circuit, driven by the potential difference created by the power source. Therefore, the electrical circuit itself is the source of electrons in a closed circuit.

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• 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.

C. Atoms in the light bulb filament.
Explanation
The correct answer is "atoms in the light bulb filament." When an incandescent light bulb is connected to a power source, the electrical current passes through the filament inside the bulb. The filament is usually made of tungsten or another metal that has a high melting point. As the current flows through the filament, it heats up and becomes white-hot, emitting light. The atoms in the filament are responsible for the emission of electrons, which generate the light in the bulb.

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• 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.

A. Woman's body.
Explanation
When a woman experiences an electrical shock, the electrons that cause the shock come from her own body. This is because our bodies can store and conduct electricity. When there is a difference in electrical potential between two parts of the body or between the body and an external object, electrons can flow through the body, resulting in an electrical shock.

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• 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

A. A fraction of a centimeter per second.
Explanation
In a common dc circuit, electrons move at speeds of a fraction of a centimeter per second. This is because in a dc circuit, the flow of electrons is relatively slow compared to the speed of light or sound waves. The movement of electrons is hindered by the resistance of the circuit components, which slows down their speed. Therefore, the speed at which electrons move in a dc circuit is only a fraction of a centimeter per second.

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• 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.

D. Less than 1 cm/s.
Explanation
When a light switch is turned on in a DC circuit, the average speed of electrons in the lamp is less than 1 cm/s. This is because in a DC circuit, the flow of electrons is relatively slow compared to other forms of energy transfer, such as the speed of sound waves in metal or the speed of light. The speed of electrons is determined by the voltage and resistance in the circuit, and in most cases, it is much slower than the speed of sound waves or light. Additionally, the speed of electrons is dependent on how quickly each electron bumps into the next electron, which further contributes to the slower average speed.

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• 19.

### Alternating current is normally produced by a

• A.

Battery.

• B.

Generator.

• C.

Both of these

• D.

Neither of these

B. Generator.
Explanation
Alternating current is normally produced by a generator. A battery is not capable of producing alternating current as it provides direct current. On the other hand, a generator converts mechanical energy into electrical energy, producing alternating current. Therefore, a generator is the correct answer for the given question.

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• 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.

E. 240 watts.
Explanation
The electric power of a lamp can be calculated using the formula P = IV, where P is the power, I is the current, and V is the voltage. In this case, the lamp carries 2 A at 120 V. Plugging these values into the formula, we get P = 2 A * 120 V = 240 watts. Therefore, the correct answer is 240 watts.

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• 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

B. Less than the resistance of either lamp.
Explanation
When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is less than the resistance of either lamp. This is because in a parallel circuit, the total resistance is less than the smallest individual resistance. Therefore, the battery senses a lower overall resistance when the lamps are connected in parallel.

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• 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

A. More than the resistance of either lamp.
Explanation
When two lamps are connected in series to a battery, the electrical resistance that the battery senses is more than the resistance of either lamp. This is because in a series circuit, the total resistance is equal to the sum of the individual resistances. Therefore, when the two lamps are connected in series, their resistances add up, resulting in a higher total resistance that the battery senses.

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• 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.

C. Series.
Explanation
In a series connection, the components are connected in a sequential manner, such that the current flows through one component before reaching the other. Therefore, if one bulb burns out in a series-connected circuit, it breaks the flow of current and causes both headlights to go out. This is different from a parallel connection, where each component has its own separate path for current flow, allowing the other bulb to continue functioning even if one burns out.

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• 24.

### Modern automobile headlights are connected in

• A.

Parallel.

• B.

Perpendicular.

• C.

Series.

• D.

None of these

A. Parallel.
Explanation
Automobile headlights are connected in parallel because they are designed to operate independently of each other. When headlights are connected in parallel, each headlight has its own separate circuit and power source. This means that if one headlight were to malfunction or burn out, the other headlight would still continue to function properly. Additionally, connecting headlights in parallel allows for equal voltage distribution, ensuring that both headlights receive the same amount of power and brightness.

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• 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.

B. The same electrons.
Explanation
When you turn on the lamp, the filament heats up and becomes incandescent. This causes the electrons in the filament to gain energy and move to higher energy levels. As they return to their original energy levels, they release this excess energy in the form of light. Therefore, the glowing of the lamp comes from the same electrons present in the filament.

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• 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.

A. Less.
Explanation
The brightness of a lamp is determined by the amount of power it consumes. A 100-Watt lamp consumes more power than a 25-Watt lamp, indicating that it converts more electrical energy into light energy. This means that the 100-Watt lamp must have a lower electrical resistance compared to the 25-Watt lamp. A lower resistance allows more current to flow through the lamp, resulting in a brighter glow. Therefore, the electrical resistance of the 100-Watt lamp must be less.

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• 27.

### In an electric circuit, the safety fuse is connected to the circuit in

• A.

Series.

• B.

Parallel.

• C.

Either series or parallel.

A. Series.
Explanation
In an electric circuit, the safety fuse is connected in series. This means that the fuse is placed in the path of the current flow, allowing it to break the circuit and prevent excessive current from damaging the components. Connecting the fuse in parallel would not provide the same level of protection, as it would allow the current to bypass the fuse and potentially cause damage. Therefore, connecting the safety fuse in series is the correct choice for ensuring the safety of the circuit.

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• 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

D. 2 ohms, and when in parallel, 1/2 ohm.
Explanation
When two 1-ohm resistors are connected in series, their combined resistance is 2 ohms because in a series circuit, the total resistance is the sum of the individual resistances. When the same resistors are connected in parallel, their combined resistance is 1/2 ohm because in a parallel circuit, the total resistance is given by the reciprocal of the sum of the reciprocals of the individual resistances.

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• 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.

B. Fuse.
Explanation
A circuit breaker often serves the same purpose as a fuse. A fuse is a safety device that protects electrical circuits from excessive current by melting and breaking the circuit when there is a fault. Similarly, a circuit breaker automatically interrupts the flow of electricity when it detects an overload or short circuit, thereby protecting the circuit from damage. Both the fuse and circuit breaker have the same function of preventing electrical fires and protecting electrical equipment.

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• 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.

C. Smoothing pulsed current.
Explanation
A capacitor is useful in smoothing pulsed current because it can store electrical energy and release it when needed. When a pulsed current is applied to a circuit, the capacitor charges up during the high points of the pulses and then discharges during the low points, effectively smoothing out the fluctuations in the current. This helps to provide a more stable and consistent flow of current in the circuit.

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• 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.

E. Changing ac to dc.
Explanation
An electrical diode is a device that allows current to flow in only one direction. It acts as a rectifier, converting alternating current (AC) to direct current (DC). This is achieved by allowing the positive half-cycles of the AC signal to pass through while blocking the negative half-cycles. Therefore, the diode is useful for changing AC to DC, making it the correct answer.

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• 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

C. 110 joules of energy are given up by each coulomb of charge making up the current in the circuit.
Explanation
The correct answer is 110 joules of energy are given up by each coulomb of charge making up the current in the circuit. In a series circuit, the current remains constant throughout, so each coulomb of charge passing through the lamp gives up the same amount of energy. This energy is converted to heat and light in the circuit.

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• 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

C. A generator.
Explanation
In a simple circuit containing a bulb, energy is given to the moving charges by a generator. This is because a generator converts mechanical energy into electrical energy, which is then supplied to the bulb. The bulb acts as a load and converts the electrical energy into light and heat. The wires in the circuit simply serve as conduits for the flow of electrical current.

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• 34.

### A capacitor is used to store

• A.

Both charge and energy.

• B.

Energy.

• C.

Charge.

• D.

Neither charge nor energy.

A. Both charge and energy.
Explanation
A capacitor is an electronic component that stores electrical energy in an electric field. When a voltage is applied across the capacitor, it accumulates charge on its plates, thus storing both charge and energy. The charge is stored in the form of electrons on the capacitor plates, while the energy is stored in the electric field between the plates. Therefore, the correct answer is that a capacitor is used to store both charge and energy.

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• 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

A. Zero.
Explanation
The explanation for the correct answer, zero, is that the question is referring to the number of electrons delivered to an average American home. While power utilities do deliver electricity to homes, it is important to understand that electricity is the flow of electrons through a circuit. The number of electrons delivered is not a relevant measure of the amount of electricity consumed by a home. Therefore, the correct answer is zero, as the question is asking for the number of electrons delivered, which is not a meaningful quantity to measure in this context.

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• 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.

C. The same in each lamp.
Explanation
When two lamps are connected in series, they share the same current. This is because the current has only one path to flow through, and it must pass through both lamps. The resistance of the filament in each lamp does not affect the current flowing through them. Therefore, the current is the same in each lamp, regardless of whether the filament is thick or thin.

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• 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.

C. The same in both lamps.
Explanation
When lamps are connected in parallel, they are connected to the same voltage source. This means that the potential difference across each lamp is equal to the voltage of the battery. Therefore, the voltage is the same in both lamps, regardless of the thickness of the filament.

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• 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.

A. Larger in the lamp with the thick filament.
Explanation
The current is larger in the lamp with the thick filament because the resistance of the thick filament is lower compared to the thin filament. According to Ohm's Law, current is inversely proportional to resistance, so a lower resistance will result in a larger current. Since the lamps are connected in parallel, the same voltage is applied across both lamps, but the lamp with the thick filament allows more current to flow through it due to its lower resistance.

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• 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.

B. Greater across the lamp with the thin filament.
Explanation
When lamps are connected in series, the total voltage of the battery is divided among the lamps. The voltage across each lamp is directly proportional to its resistance. Since the lamps are made of the same material, the lamp with the thicker filament will have a lower resistance compared to the lamp with the thinner filament. According to Ohm's law (V = IR), a lower resistance will result in a higher voltage across the lamp. Therefore, the voltage is greater across the lamp with the thin filament.

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• 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.

B. Decreases.
Explanation
When more lamps are added to a series circuit, the overall resistance in the circuit increases. According to Ohm's Law (V = IR), if the resistance increases and the voltage remains constant, the current flowing through the circuit will decrease. Therefore, as more lamps are added in series, the overall current in the power source decreases.

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• 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.

A. Increases.
Explanation
When lamps are connected in parallel, each lamp has its own separate path for current to flow. This means that as more lamps are added, more paths are created for the current to pass through. As a result, the overall current in the power source increases because the total resistance of the circuit decreases.

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• 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

D. Through both the battery and the rest of the circuit.
Explanation
When a circuit is powered with a battery, charge flows through both the battery and the rest of the circuit. This means that the electrons move from the negative terminal of the battery, through the circuit, and eventually reach the positive terminal of the battery. This flow of charge allows for the transfer of energy and the operation of the circuit.

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• 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.

E. Electron kinetic energy is changed into heat.
Explanation
When we say an appliance "uses up electricity," it means that the electrical energy is converted into another form of energy, specifically heat. This happens because the flow of electrons through the appliance's circuit creates kinetic energy, which is then transformed into heat energy due to resistance in the circuit.

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• 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.

B. Less resistance.
Explanation
When resistors are connected in series, their resistances add up, resulting in a higher total resistance. However, when resistors are connected in parallel, the total resistance is lower than the resistance of each individual resistor. This is because the current has multiple paths to flow through, reducing the overall resistance. Therefore, the correct answer is "less resistance."

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• 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.

D. Twice what it should be.
Explanation
When you plug an electric toaster rated at 110 V into a 220-V outlet, the current in the toaster will be twice what it should be. This is because the voltage difference between the toaster's rating and the outlet's voltage is twice the toaster's rating. According to Ohm's Law (V = I * R), when the voltage increases, the current also increases, given that the resistance remains the same. Therefore, the current in the toaster will be twice what it should be in this scenario.

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• 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.

B. 0.5 A.
Explanation
The current in a circuit can be calculated using Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the resistance of the light bulb is not given, but we can assume it is constant. Therefore, when the voltage is doubled from 120 volts to 240 volts, the current is halved. Since the current is halved, it would be 0.5 A when the light bulb is connected to a 120-volt source.

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• 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.

D. 96 W.
Explanation
The power consumed by an electrical device can be calculated using the formula P = IV, where P is power, I is current, and V is voltage. In this case, the current is given as 0.8 A and the voltage is 120 V. Plugging these values into the formula, we get P = 0.8 A * 120 V = 96 W. Therefore, the correct answer is 96 W.

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• 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.

B. Parallel with a switch for each.
Explanation
In an automobile, the headlights, radio, and defroster fan are connected in parallel with a switch for each. This means that each component has its own switch, allowing them to be operated independently. In a parallel circuit, the components are connected in such a way that the current has multiple paths to flow through. Therefore, turning on or off one component does not affect the others. This arrangement allows the driver to control each component individually without interfering with the functioning of the others.

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• 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.

A. 2.4 ohms.
Explanation
When resistors are connected in parallel, the equivalent resistance is calculated using the formula 1/Req = 1/R1 + 1/R2 + 1/R3 + ... In this case, the formula becomes 1/Req = 1/4 + 1/6. Solving this equation gives the value of Req as 2.4 ohms, which is the equivalent resistance of the combination.

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• 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.

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