phys 222, chapter 18 (exam 2)

To find the equivalent resistance of the combination of resistors shown across the 28-V battery by the method of possibly repeated applications of combining resistors in series and /or combining resistors in parallel, the first step would be which of the following? a. Combine the two 10 Ω in parallel since they can be done in your head. b. Combine, in series, the two 3-Ω resistors and the 4-Ω resistor in the right-hand branch of the circuit. c. Combine the seven resistors (two 5 Ω, three 3 Ω, one 2 Ω and one 4 Ω) in the outer loop of the circuit in series. d. This problem cannot be done by combining series and parallel resistors.

b

Two resistors of values 6.0 and 12.0 Ω are connected in parallel. This combination in turn is hooked in series with a 2.0-Ω resistor and a 24-V battery. What is the current in the 2-Ω resistor? a. 2.0 A b. 4.0 A c. 6.0 A d. 12 A

b

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

b

What is the equivalent resistance for these 3.00-W resistors? a. 1.33 W b. 2.25 W c. 3.00 W d. 7.50 W

b

When a 24.0-Ω resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the internal resistance of the battery? a. 0.02 Ω b. 0.9 Ω c. 25.0 Ω d. 49.8 Ω

b

Which two resistors are in parallel with each other? a. R and R4 b. R2 and R3 c. R2 and R4 d. R and R1

b

A 1 000-V battery, a 3 000-Ω resistor, and a 0.50-mF capacitor are connected in series with a switch. The time constant for such a circuit, designated by the Greek letter, t, is defined as the time that the capacitor takes to charge to 63% of its capacity after the switch is closed. What is the current in the circuit at a time interval of t seconds after the switch has been closed? a. 0.14 A b. 0.21 A c. 0.12 A d. 0.32 A

c

A 10-V-emf battery is connected in series with the following: a 2-μF capacitor, a 2-Ω 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? a. zero A, 10 V b. zero A, zero V c. 5 A, zero V d. 5 A, 10 V

c

A circuit contains a 6.0-V battery, a 4.0-Ω 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? a. zero b. 0.75 A c. 1.5 A d. 10 A

c

A circuit contains a 6.0-V battery, a 4.0-Ω 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? a. zero b. 0.10 μC c. 3.6 μC d. 2.4 μC

c

Consider the circuit shown in the figure. What power is dissipated by the entire circuit? a. 14 W b. 28 W c. 52 W d. 112 W

c

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.

c

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? a. 8.0 V + I1R1 + I3R3 = 0 b. 8.0 V + I1R1 - I3R3 = 0 c. 8.0 V - I1R1 + I3R3 = 0 d. -8.0 V + I1R1 + I3R3 = 0

c

If R1 < R2 < R3, and if these resistors are connected in series in a circuit, which one dissipates the greatest power? a. R1 b. R2 c. R3 d. All are equal in power dissipation.

c

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.

c

Resistors of values 6.0W, 4.0W, 10.0W and 7.0W are combined as shown. What is the equivalent resistance for this combination? a. 2.3 W b. 3.0 W c. 10.7 W d. 27 W

c

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? a. the 8.0-W resistor b. the 12.0-W resistor c. the 24.0-W resistor d. The answer depends on the internal resistance of the battery.

c

The two ends of a 3.0-W resistor are connected to a 9.0-V battery. What is the current through the resistor? a. 27 A b. 6.3 A c. 3.0 A d. 0.33 A

c

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? a. 16 A b. 9.0 A c. 3.0 A d. 48 A

c

Three resistors connected in parallel have the individual voltages labeled ΔV1, ΔV2 and ΔV3, respectively. Which of the following expresses the total voltage ΔVT across the three resistors when connected in this manner? a. ΔVT = ΔV1 + ΔV2 + ΔV3 b. ΔVT = (1/ΔV1 + 1/ΔV2 + 1/ΔV3) c. ΔVT = ΔV1 = ΔV2 = ΔV3 d. ΔVT = (1/ΔV1 + 1/ΔV2 + 1/ΔV3)-1

c

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? a. IT = I1 + I2 + I3 b. IT = (1/I1 + 1/I2 + 1/I3) c. IT = I1 = I2 = I3 d. IT = (1/I1 + 1/I2 + 1/I3)-1

c

To find the equivalent resistance of the combination of resistors shown below by the method of possibly repeated applications of combining resistors in series and /or combining resistors in parallel, the first step would be which of the following? a. Combine the 6.0 Ω and the 7.0 Ω in series. b. Combine either the 4.0 Ω and the 10.0 Ω in parallel or the 7.0 Ω and the 10.0 Ω in parallel first, since either could be the first step with the other the second step. c. Combine the 4.0 Ω and the 10.0 Ω in series. d. Combine the 6.0 Ω, the 4.0 Ω, and the 10.0 Ω in series in a single step.

c

Two resistors of values 6.0 and 12.0 Ω are connected in parallel. This combination in turn is hooked in series with a 4.0-Ω resistor. What is the overall resistance of this combination? a. 0.50 Ω b. 2.0 Ω c. 8.0 Ω d. 22.0 Ω

c

What is the current flowing through the 2-Ω resistor? a. 2 A b. 3 A c. 4 A d. 6 A

c

What is the current through the 8-Ω resistor? a. 1.0 A b. 0.50 A c. 1.5 A d. 2.0 A

c

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

c

What is the potential difference between points a and b? a. 6 V b. 8 V c. 12 V d. 24 V

c

When a 24.0-Ω resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the resulting terminal voltage of the battery? a. 0.4 V b. 5.8 V c. 11.6 V d. 12.0 V

c

When a 24.0-Ω 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? a. 0.21 W b. 5.57 W c. 5.78 W d. 6.00 W

c

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? a. It stays constant. b. It increases. c. It decreases. d. It increases at first and then decreases.

c

A 10-V-emf battery is connected in series with the following: a 2-mF capacitor, a 2-Ω resistor, an ammeter, and a switch, initially open; a voltmeter is connected in parallel across the capacitor. After the switch has been closed for a relatively long period (several seconds, say), what are the current and capacitor voltage readings, respectively? a. zero A, 10 V b. zero A, zero V c. 5 A, zero V d. 5 A, 10 V

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? a. 0.43 C b. 0 66 C c. 0.86 C d. 0.99 C

a

How much current is flowing in one of the 10-W resistors? a. 0.8 A b. 2.0 A c. 1.6 A d. 2.4 A

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. a. 1.5 mC, left plate is positive b. 1.5 mC, right plate is positive c. 0.50 mC, left plate is positive d. 0.50 mC, right plate is positive

a

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? a. I1 + I2 + I3 = 0 b. I1 + I2 - I3 = 0 c. I1 - I2 + I3 = 0 d. I1 - I2 - I3 = 0

a

If R1 < R2 < R3, and if these resistors are connected in parallel in a circuit, which one has the highest current? a. R1 b. R2 c. R3 d. All have the same current.

a

If e = 24 V, at what rate is thermal energy generated in the 20-Ω resistor? a. 13 W b. 3.2 W c. 23 W d. 39 W

a

If e = 9.0 V, what is the current in the 15-Ω resistor? a. 0.20 A b. 0.30 A c. 0 10 A d. 0.26 A

a

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. a. They stay the same. b. They double. c. They quadruple. d. They halve.

a

Resistors having values of , , and are connected in series in the order given.The combination is then connected to a battery with the free end of the 4.0-Ω resistor connected to the positive terminal and the free end of the 8.0-Ω resistor connected to the negative terminal. When connected, the battery has a terminal voltage of . If the battery is disconnected, its terminal voltage is 9.4 V. When the battery is connected, what is the power dissipated by the internal resistance? a. 0.2 W b. 0.4 W c. 3 W d. 0.3 W

a

Resistors of values 8.0 Ω, 12.0 Ω, and 24.0 Ω are connected in parallel across a fresh battery. Which resistor dissipates the greatest power? a. the 8.0-Ω resistor b. the 12.0-Ω resistor c. the 24.0-Ω resistor d. All dissipate the same power when in parallel.

a

Three 8.0-Ω resistors are connected in series. What is their equivalent resistance? a. 24.0 Ω b. 8.0 Ω c. 0.38 Ω d. 0.13 Ω

a

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? a. IT = I1 + I2 + I3 b. IT = (1/I1 + 1/I2 + 1/I3) c. IT = I1 = I2 = I3 d. IT = (1/I1 + 1/I2 + 1/I3)-1

a

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? a. 0.59 A b. 1.0 A c. 11 A d. 16 A

a

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? a. DVT = DV1 + DV2 + DV3 b. DVT = (1/DV1 + 1/DV2 + 1/DV3) c. DVT = DV1 = DV2 = DV3 d. DVT = (1/DV1 + 1/DV2 + 1/DV3)-1

a

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? a. RT = R1 + R2 + R3 b. RT = (1/R1 + 1/R2 + 1/R3) c. RT = R1 = R2 = R3 d. RT = (1/R1 + 1/R2 + 1/R3)-1

a

Three resistors, each with resistance R1, are in series in a circuit. They are replaced by one equivalent resistor, R. Comparing this resistor to the first resistor of the initial circuit, which of the following is true? a. The current through R equals the current through R1. b. The voltage across R equals the voltage across R1. c. The power given off by R equals the power given off by R1. d. R is less than R1.

a

Two resistors of values 6.0 and 12.0 Ω are connected in parallel. This combination in turn is hooked in series with a 4.0-Ω resistor and a 24-V battery. What is the current in the 6-Ω resistor? a. 2.0 A b. 3.0 A c. 6.0 A d. 12 A

a

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

a

What is the current flowing through the 4-Ω resistor? a. 1 A b. 2 A c. 3 A d. 6 A

a

What is the current through the 2-Ω resistor? a. 1.0 A b. 0.50 A c. 1.5 A d. 2.0 A

a

Which voltage is not caused by a source of emf? a. the voltage across a charged capacitor b. the voltage across two copper-iron junctions at different temperatures c. the voltage across the terminals of a dry cell battery d. the voltage from an electric generator

a

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 Ω and the current through it is 0.40 A. What is the value of the other resistor? a. 8.0 Ω b. 16 Ω c. 24 Ω d. 32 Ω

b

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

b

Resistors having values of , , and are connected in series in the order given. The combination is then connected to a battery with the free end of the 4.0-Ω resistor connected to the positive terminal and the free end of the 8.0-Ω resistor connected to the negative terminal. When connected, the battery has a terminal voltage of . If the negative battery terminal has an electric potential of , what is the potential at the connection between the 4.0-Ω and the 8.0-Ω resistors? a. 7.2 V b. 7.0 V c. 4.0 V d. 7.4 V

b

Resistors having values of , , and are connected in series in the order given.The combination is then connected to a battery with the free end of the 4.0-Ω resistor connected to the positive terminal and the free end of the 8.0-Ω resistor connected to the negative terminal. When connected, the battery has a terminal voltage of . If the battery is disconnected, its terminal voltage is 9.4 V. What is the internal resistance of the battery? a. 0.4 b. 0.8 c. 0.05 d. 0.02

b

The basic function of an electromotive force in a circuit is to do which of the following? a. Convert electrical energy into some other form. b. Convert some other form of energy into electrical. c. Both choices (a) and (b) are valid. d. None of the above choices are valid.

b

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? a. 3.0 W b. 27 W c. 0.33 W d. 0.11 W

b

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.

b

Three resistors, each with resistance R1, are in parallel in a circuit. They are replaced by one equivalent resistor, R. Compare this resistor to the first resistor of the initial circuit. Which of the following statements is true? a. The current through R equals the current through R1. b. The voltage across R equals the voltage across R1. c. The power given off by R equals the power given off by R1. d. R is greater than R1.

b

Three resistors, with values of 2.0, 4.0 and 8.0 Ω, respectively, are connected in parallel. What is the overall resistance of this combination? a. 0.58 Ω b. 1.1 Ω c. 7.0 Ω d. 14.0 Ω

b

Three resistors, with values of 2.0, 4.0 and 8.0 W, respectively, are connected in series. What is the overall resistance of this combination? a. 0.58 W b. 1.1 W c. 7.0 W d. 14.0 W

d

What is Kirchhoff's 1st equation for this junction? a. I1 = I2 + I3 b. I2 = I1+ I2 c. I3 = I1 + I2 d. I1 + I2 + I3 = 0

d

Which resistor is in series with resistor R? a. R1 b. R2 c. R3 d. R4

d

If e = 20 V, at what rate is thermal energy being generated in the 20-Ω resistor? a. 6.5 W b. 1.6 W c. 15 W d. 26 W

b

A 1 000-V battery, a 3 000-Ω 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? a. 0.39 A b. 0.33 A c. 0.84 A d. 2 000 A

b

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

b

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.

b

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 Ω? a. 1.1 h b. 2.2 h c. 4.1 h d. 13 h

b

Household circuits are wired in ________. a. series b. parallel c. both series and parallel d. neither series nor parallel

b

A 1 000-V battery, a 3 000-Ω resistor and a 0.50-μF capacitor are connected in series with a switch. The time constant for such a circuit, designated by the Greek letter, t, is defined as the time required to charge the capacitor to 63% of its capacity after the switch is closed. What is the value of t for this circuit? a. 6.0 ́ 109 s b. 1.7 ́ 10-10 s c. 1.7 ́ 10-7 s d. 1.5 ́ 10-3 s

d

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: a. the size of the capacitor. b. the size of the resistor. c. the size of the time constant. d. None of the above.

d

A voltage source of 10 V is connected to a series RC circuit where R = 2.0 ́ 106 Ω, 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

d

How much power is being dissipated by one of the 10-W resistors? a. 24 W b. 9.6 W c. 16 W d. 6.4 W

d

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

d

In the circuit segment shown if I = 7 mA and Q = 50 μC, what is the potential difference, VA - VB? a. -40 V b. +40 V c. +20 V d. -20 V

d

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

d

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): a. zero and zero. b. infinite and infinite. c. zero and infinite. d. infinite and zero.

d

Three 8.0-W resistors are connected in parallel. What is their equivalent resistance? a. 0.054 W b. 0.13 W c. 0.38 W d. 2.7 W

d

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? a. RT = R1 + R2 + R3 b. RT = (1/R1 + 1/R2 + 1/R3) c. RT = R1 = R2 = R3 d. RT = (1/R1 + 1/R2 + 1/R3)-1

d