Physics Midterm Chapter 18

In the circuit segment shown if I = 7 mA and Q = 50 µC, what is the potential difference, VA - VB?

-20 V

If e = 9.0 V, what is the current in the 15-W resistor?

0.20 A

A 1 000-V battery, a 3 000-W resistor and a 0.50-µF capacitor are connected in series with a switch. The capacitor is initially uncharged. What is the value of the current the moment after the switch is closed?

0.33 A

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?

0.43 C

Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 W, respectively. If this combination is connected in series with a 12-V battery and a 2.0-W resistor, what is the current in the 10-W resistor?

0.59 A

ow much current is flowing in one of the 10-W resistors?

0.8 A

When a 24.0-W resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the internal resistance of the battery?

0.9 W

Three resistors, with values of 2.0, 4.0 and 8.0 W, respectively, are connected in parallel. What is the overall resistance of this combination?

1.1 W

A circuit contains a 6.0-V battery, a 4.0-W resistor, a 0.60-µF capacitor, an ammeter, and a switch all in series. What will be the current reading immediately after the switch is closed?

1.5 A

What is the current through the 8-W resistor?

1.5 A

If I = 2.0 mA and the potential difference, VA - VB = +30 V in the circuit segment shown, determine the charge and polarity of the capacitor.

1.5 mC, left plate is positive

If e = 20 V, at what rate is thermal energy being generated in the 20-W resistor?

1.6 W

When a 24.0-W resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the resulting terminal voltage of the battery?

11.6 V

If e = 24 V, at what rate is thermal energy generated in the 20-W resistor?

13 W

In a circuit, a current of 2.0 A is drawn from a battery. The current then divides and passes through two resistors in parallel. One of the resistors has a value of 64 W and the current through it is 0.40 A. What is the value of the other resistor?

16 W

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.

18 s

Two resistors of values 6.0 and 12.0 W are connected in parallel. This combination in turn is hooked in series with a 4.0-W resistor and a 24-V battery. What is the current in the 6-W resistor?

2.0 A

Four 1.5-volt AA batteries in series power a transistor radio. If the batteries hold a total charge of 240 C, how long will they last if the radio has a resistance of 200 W?

2.2 h

What is the equivalent resistance for these 3.00-W resistors?

2.25 W

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?

20.8 A

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?

23 A

The two ends of a 3.0-W resistor are connected to a 9.0-V battery. What is the total power delivered by the battery to the circuit?

27 W

The two ends of a 3.0-W resistor are connected to a 9.0-V battery. What is the current through the resistor?

3.0 A

Three 4.0-W resistors are connected in parallel to a 12.0-V battery. What is the current in any one of the resistors?

3.0 A

A circuit contains a 6.0-V battery, a 4.0-W resistor, a 0.60-µF capacitor, an ammeter, and a switch in series. What will be the charge on the capacitor 10 min after the switch is closed?

3.6 µC

What is the current flowing through the 2-W resistor?

4 A

Two resistors of values 6.0 and 12.0 W are connected in parallel. This combination in turn is hooked in series with a 2.0-W resistor and a 24-V battery. What is the current in the 2-W resistor?

4.0 A

A 10-V-emf battery is connected in series with the following: a 2-µF capacitor, a 2-W resistor, an ammeter, and a switch, initially open; a voltmeter is connected in parallel across the capacitor. At the instant the switch is closed, what are the current and capacitor voltage readings, respectively?

5 A, zero V

When a 24.0-W resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the power output delivered by the emf of the battery?

5.78 W

Consider the circuit shown in the figure. What power is dissipated by the entire circuit?

52 W

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?

59

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?

6.0 ms

How much power is being dissipated by one of the 10-W resistors?

6.4 W

If I1 goes to the right through R1, I2 goes to the right through R2, and I3 goes to the right through R3, what is the resulting equation resulting from applying Kirchhoff's loop rule for a clockwise loop around the perimeter of the circuit?

8.0 V - I1R1 + I3R3 = 0

The basic function of an electromotive force in a circuit is to do which of the following?

Convert some other form of energy into electrical.

Three resistors connected in series have individual voltages labeled DV1, DV2 and DV3, respectively. Which of the following expresses the value of the total voltage DVT taken over the three resistors together?

DVT = DV1 + DV2 + DV3

Three resistors connected in parallel have the individual voltages labeled DV1, DV2 and DV3, respectively. Which of the following expresses the total voltage DVT across the three resistors when connected in this manner?

DVT = DV1 = DV2 = DV3

If I1 goes to the right through R1, I2 goes to the right through R2, and I3 goes to the right through R3, what is the resulting equation resulting from applying Kirchhoff's junction rule at point b?

I1 + I2 + I3 = 0

What is Kirchhoff's 1st equation for this junction?

I1 + I2 + I3 = 0

Three resistors connected in parallel each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the combined system?

IT = I1 + I2 + I3

Three resistors connected in series each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the system made up of the three resistors in series?

IT = I1 = I2 = I3

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?

It connects the case of the appliance directly to ground for safety purposes.

When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the current in the bulb as it is warming up?

It decreases.

Household circuits are wired in ____.

Parallel

If R1 < R2 < R3, and if these resistors are connected in parallel in a circuit, which one has the highest current?

R1

Which two resistors are in parallel with each other?

R2 and R3

If R1 < R2 < R3, and if these resistors are connected in series in a circuit, which one dissipates the greatest power?

R3

Which resistor is in series with resistor R?

R4

Three resistors with values R1, R2 and R3, respectively, are connected in parallel. Which of the following expresses the total resistance, RT, of the three resistors when connected in parallel?

RT = (1/R1 + 1/R2 + 1/R3)^-1

Three resistors with values of R1, R2 and R3, respectively, are connected in series. Which of the following expresses the total resistance, RT, of the three resistors?

RT = R1 + R2 + R3

If one doubles the emfs in a circuit and doubles the resistances in the circuit at the same time, what happens to the currents through the resistors? Assume there are only emfs and resistors in the circuit.

They stay the same.

Resistors of values 8.0 W, 12.0 W, and 24.0 W are connected in parallel across a fresh battery. Which resistor dissipates the greatest power?

the 8.0-W resistor

Which voltage is not caused by a source of emf?

the voltage across a charged capacitor

Resistors of values 8.0 W, 12.0 W, and 24.0 W are connected in series across a battery with a small internal resistance. Which resistor dissipates the greatest power?

the 24.0-W resistor

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?

ground-fault interrupter

The internal resistances of an ideal voltmeter and an ideal ammeter are respectively (ideal meaning the behavior of the system is not changed when using the meter):

infinite and zero

A certain capacitor is charged to 10 V and then, at t = 0, allowed to discharge through a certain resistor. There will be a certain time before the voltage across the capacitor reaches 5 V. This time can be decreased for this circuit by increasing:

none of the above.