Question 1

In applications where electrical shocks may be more likely, such as around water in kitchens and bathrooms, special outlets called GFI's are used.What does GFI stand for?
A)get free instantly
B)ground-fault interrupter
C)give fast interruption
D)gravity-free insulator

Accepted Answer

GFI stands for ground-fault interrupter, which is a type of outlet that is designed to protect against electrical shocks in areas where water is present, such as kitchens and bathrooms. It works by detecting imbalances in the electrical current and quickly shutting off power to the outlet in the event of a ground fault.

Question 2

The following three appliances are connected to a 120-V house circuit: i) toaster, 1 200 W, ii) coffee pot, 750 W, and iii) microwave, 800 W.If all were operated at the same time, what total current would they draw?
A)3.0 A
B)5.0 A
C)10 A
D)23 A

Accepted Answer

To find the total current, we need to use the formula: 
Current (I) = Power (P) / Voltage (V)

For the toaster: I = 1200 W / 120 V = 10 A
For the coffee pot: I = 750 W / 120 V = 6.25 A
For the microwave: I = 800 W / 120 V = 6.67 A

Adding these three currents together, we get:
Total current = 10 A + 6.25 A + 6.67 A = 23 A

Therefore, the best choice is D.

Question 3

What is the maximum number of 60-W light bulbs you can connect in parallel in a 120-V home circuit without tripping the 30-A circuit breaker?
A)11
B)35
C)59
D)3 600

Accepted Answer

The answer of What is the maximum number of 60-W...

Question 4

A hair dryer draws 1 200 W, a curling iron draws 800 W, and an electric light fixture draws 500 W.If all three of these appliances are operating in parallel on a 120-V circuit, what is the total current drawn?
A)19.4 A
B)20.8 A
C)25.4 A
D)36.7 A

Accepted Answer

The answer of A hair dryer draws 1 200 W,...

Question 5

A voltage source of 10 V is connected to a series RC circuit where R = 2.0 * 10⁶ W, and C = 3.0 µF.Find the amount of time required for the current in the circuit to decay to 5% of its original value. Hint: This is the same amount of time for the capacitor to reach 95% of its maximum charge. A)3.0 s B)6.0 s C)9.0 s D)18 s

Accepted Answer

The answer of A voltage source of 10 V is...

Question 6

A series RC circuit, which is made from a battery, a switch, a resistor, and a 3.0-mF capacitor, has a time constant of 9.0 ms.If an additional 6.0-mF is added in series to the 3.0-mF capacitor, what is the resulting time constant?
A)4.0 ms
B)6.0 ms
C)10 ms
D)This cannot be found without the value of the resistance being given.

Accepted Answer

The answer of A series RC circuit, which is made...

Question 7

Using a capacitor and two different value resistors, which of the following combinations in an RC circuit would give the greatest time constant?
A)the capacitor in series with both resistors in series with each other
B)the capacitor in series with both resistors in parallel with each other
C)the capacitor in series with the higher value resistor
D)the capacitor in series with the lower value resistor

Accepted Answer

The time constant ($\tau$) of an RC circuit is given by $\tau = RC$, where $R$ is the resistance and $C$ is the capacitance. In option A, the resistors in series combine their resistances, resulting in a higher total resistance compared to the other configurations, thus giving the greatest time constant.

Question 8

Using a resistor and two different value capacitors, which of the following combinations in an RC circuit would give the greatest time constant?
A)the resistor in series with both capacitors in series with each other
B)the resistor in series with both capacitors in parallel with each other
C)the resistor in series with the larger value capacitor
D)the resistor in series with the lower value capacitor

Accepted Answer

The answer of Using a resistor and two different value...

Question 9

Household 120-V outlets are made to accept three-pronged plugs.One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground.What is the round third prong for?
A)It serves as a backup to the hot wire.
B)It lets the appliance run if the neutral wire breaks.
C)It connects the case of the appliance directly to ground for safety purposes.
D)Nothing electrical, it is for mechanical sturdiness.

Accepted Answer

The round third prong is known as the ground prong and it connects the case of the appliance directly to the ground for safety purposes. This is important because if there is a fault in the appliance, such as a short circuit, the case can become energized and present a shock hazard to the user. By connecting the case to the ground, any current will be safely directed away from the user and into the ground.

Question 10

Three resistors, each of different value, are used in a circuit with a power source supplying 12 volts.For which of the following resistor combinations is the total power supplied the greatest?
A)all three resistors in series
B)all three resistors in parallel
C)two of the resistors in parallel with the third resistor in series with the parallel pair
D)This cannot be found until it is known which resistor is in series with the parallel pair.

Accepted Answer

When resistors are in parallel, the equivalent resistance is less than any individual resistor, which means the circuit draws more current from the power source. Additionally, the power dissipated in each resistor is equal to I^2*R, where I is the current through the resistor and R is the resistance. Since the current through each resistor in parallel is the same, the power dissipated in each resistor is proportional to its resistance. Therefore, the resistor with the highest resistance will dissipate the most power. In this case, since all three resistors have different values, the highest resistance will be in the highest value resistor. Thus, by placing all three resistors in parallel, the current drawn from the power source is maximized, and the resistor with the highest value is dissipating the most power, leading to the greatest total power supplied.

Question 11

In an RC circuit using two capacitors in series with two resistors, which of the following combinations would give the greatest time constant?
A)both capacitors in series placed in series with both resistors in series
B)both capacitors in parallel placed in series with both resistors in parallel
C)both capacitors in series placed in series with both resistors in parallel
D)both capacitors in parallel placed in series with both resistors in series

Accepted Answer

The time constant ($\tau$) of an RC circuit is given by $\tau = RC$, where $R$ is the resistance and $C$ is the capacitance. For capacitors in parallel, the total capacitance ($C_{total}$) is the sum of the individual capacitances ($C_{total} = C_1 + C_2$). For resistors in series, the total resistance ($R_{total}$) is the sum of the individual resistances ($R_{total} = R_1 + R_2$). Therefore, having both capacitors in parallel increases the total capacitance, and having both resistors in series increases the total resistance, which together maximize the time constant ($\tau$).

Question 12

A series RC circuit has a time constant of 1.0 s.The battery has a voltage of 50 V and the maximum current just after closing the switch is 500 mA.The capacitor is initially uncharged.What is the charge on the capacitor 2.0 s after the switch is closed? 
A)0.43 C
B)0 66 C
C)0.86 C
D)0.99 C

Accepted Answer

The answer of A series RC circuit has a time...

Question 13

Household circuits are wired in ________.
A)series
B)parallel
C)both series and parallel
D)neither series nor parallel

Accepted Answer

Household circuits are usually wired in parallel. This means each appliance has its own circuit with its own fuse or circuit breaker. If one appliance fails or trips a circuit, the other appliances can still function because they are not part of the same series circuit. Additionally, parallel circuits allow for greater flexibility in adding or removing appliances without affecting the rest of the circuit.

Question 14

Kirchhoff's rules are the junction rule and the loop rule.Which of the following statements is true?
A)Both rules are based on the conservation of charge.
B)Both rules are based on the conservation of energy.
C)The junction rule is based on the conservation of charge, and the loop rule is based on the conservation of energy.
D)The junction rule is based on the conservation of energy, and the loop rule is based on the conservation of charge.

Accepted Answer

The junction rule is based on the conservation of charge, which states that the total current entering a junction is equal to the total current leaving it. The loop rule is based on the conservation of energy, which states that the total potential difference around any closed loop in a circuit is equal to the sum of the potential differences across each component in that loop.

Quiz 18: Direct-Current Circuits

In applications where electrical shocks may be more likely, such as around water in kitchens and bathrooms, special outlets called GFI's are used.What does GFI stand for?

The following three appliances are connected to a 120-V house circuit: i) toaster, 1 200 W, ii) coffee pot, 750 W, and iii) microwave, 800 W.If all were operated at the same time, what total current would they draw?

What is the maximum number of 60-W light bulbs you can connect in parallel in a 120-V home circuit without tripping the 30-A circuit breaker?

A hair dryer draws 1 200 W, a curling iron draws 800 W, and an electric light fixture draws 500 W.If all three of these appliances are operating in parallel on a 120-V circuit, what is the total current drawn?

A voltage source of 10 V is connected to a series RC circuit where R = 2.0 * 106 W, and C = 3.0 µF.Find the amount of time required for the current in the circuit to decay to 5% of its original value. Hint: This is the same amount of time for the capacitor to reach 95% of its maximum charge.

A series RC circuit, which is made from a battery, a switch, a resistor, and a 3.0-mF capacitor, has a time constant of 9.0 ms.If an additional 6.0-mF is added in series to the 3.0-mF capacitor, what is the resulting time constant?

Using a capacitor and two different value resistors, which of the following combinations in an RC circuit would give the greatest time constant?

Using a resistor and two different value capacitors, which of the following combinations in an RC circuit would give the greatest time constant?

Household 120-V outlets are made to accept three-pronged plugs.One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground.What is the round third prong for?

Three resistors, each of different value, are used in a circuit with a power source supplying 12 volts.For which of the following resistor combinations is the total power supplied the greatest?

In an RC circuit using two capacitors in series with two resistors, which of the following combinations would give the greatest time constant?

A series RC circuit has a time constant of 1.0 s.The battery has a voltage of 50 V and the maximum current just after closing the switch is 500 mA.The capacitor is initially uncharged.What is the charge on the capacitor 2.0 s after the switch is closed?

Household circuits are wired in ________.

Kirchhoff's rules are the junction rule and the loop rule.Which of the following statements is true?

A voltage source of 10 V is connected to a series RC circuit where R = 2.0 * 10⁶ W, and C = 3.0 µF.Find the amount of time required for the current in the circuit to decay to 5% of its original value. Hint: This is the same amount of time for the capacitor to reach 95% of its maximum charge.