Chapter 27

The positive terminals of two batteries with emf's of E1 and E2, respectively, are connected together. Here E2 > E1. The circuit is completed by connecting the negative terminals. If each battery has an internal resistance r, the rate with which electrical energy is converted to chemical energy in the smaller battery is: A. E²₁ /r B. E²₁ /2r C. (E₂ − E₁)E₁/r D. (E₂ − E₁)E₁/2r E. E²₂/2r

(E₂ − E₁)E₁/2r

Four 20-Ω resistors are connected in series and the combination is connected to a 20-V emf device. The current in any one of the resistors is: A. 0.25A B. 1.0A C. 4.0A D. 5.0A E. 100A

0.25A

A 3-Ω and a 1.5-Ω resistor are wired in parallel and the combination is wired in series to a 4-Ω resistor and a 10-V emf device. The current in the 3-Ω resistor is: A. 0.33A B. 0.67A C. 2.0A D. 3.3A E. 6.7A

0.67A

Resistor 1 has twice the resistance of resistor 2. They are connected in parallel to a battery. The ratio of the thermal energy generation rate in 1 to that in 2 is: A. 1 : 4 B. 1 : 2 C. 1 : 1 D. 2 : 1 E. 4 : 1

1 : 2

Four 20-Ω resistors are connected in parallel and the combination is connected to a 20-V emf device. The current in any one of the resistors is: A. 0.25A B. 1.0A C. 4.0A D. 5.0A E. 100A

1.0A

In an antique automobile, a 6-V battery supplies a total of 48W to two identical headlights in parallel. The resistance (in ohms) of each bulb is: A. 0.67 B. 1.5 C. 3 D. 4 E. 8

1.5

Resistances of 2.0 Ω, 4.0 Ω, and 6.0 Ω and a 24-V emf device are all in parallel. The current in the 2.0-Ω resistor is: A. 12A B. 4.0A C. 2.4A D. 2.0A E. 0.50A

12A

A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its charge is half the final value. The time constant for the process is about: A. 0.43 ms B. 2.3ms C. 6.9ms D. 10 ms E. 14 ms

14 ms

Two identical batteries, each with an emf of 18V and an internal resistance of 1 Ω, are wired in parallel by connecting their positive terminals together and connecting their negative terminals together. The combination is then wired across a 4-Ω resistor. The potential difference across the 4-Ω resistor is: A. 4.0V B. 8.0V C. 14V D. 16V E. 29V

16V

A battery with an emf of 24V is connected to a 6-Ω resistor. As a result, current of 3A exists in the resistor. The terminal potential difference of the battery is: A. 0 B. 6V C. 12V D. 18V E. 24V

18V

A battery with an emf of 12V and an internal resistance of 1 Ω is used to charge a battery with an emf of 10V and an internal resistance of 1 Ω. The current in the circuit is: A. 1A B. 2A C. 4A D. 11A E. 22A

1A

Two identical batteries, each with an emf of 18V and an internal resistance of 1 Ω, are wired in parallel by connecting their positive terminals together and connecting their negative terminals together. The combination is then wired across a 4-Ω resistor. The current in each battery is: A. 1.0A B. 2.0A C. 4.0A D. 3.6A E. 7.2A

2.0A

A 3-Ω and a 1.5-Ω resistor are wired in parallel and the combination is wired in series to a 4-Ω resistor and a 10-V emf device. The potential difference across the 3-Ω resistor is: A. 2.0V B. 6.0V C. 8.0V D. 10V E. 12V

2.0V

A certain capacitor, in series with a 720-Ω resistor, is being charged. At the end of 10 ms its charge is half the final value. The capacitance is about: A. 9.6 μF B. 14 μF C. 20 μF D. 7.2F E. 10 F

20 μF

A galvanometer has an internal resistance of 12 Ω and requires 0.01A for full scale deflection. To convert it to a voltmeter reading 3V full scale, one must use a series resistance of: A. 102 Ω B. 288 Ω C. 300 Ω D. 360 Ω E. 412 Ω

288 Ω

A 120-V power line is protected by a 15-A fuse. What is the maximum number of "120V, 500W" light bulbs that can be operated at full brightness from this line? A. 1 B. 2 C. 3 D. 4 E. 5

3

Four wires meet at a junction. The first carries 4A into the junction, the second carries 5A out of the junction, and the third carries 2A out of the junction. The fourth carries: A. 7A out of the junction B. 7A into the junction C. 3A out of the junction D. 3A into the junction E. 1A into the junction

3A into the junction

Nine identical wires, each of diameter d and length L, are connected in parallel. The combination has the same resistance as a single similar wire of length L but whose diameter is: A. 3d B. 9d C. d/3 D. d/9 E. d/81

3d

By using only two resistors, R1 and R2, a student is able to obtain resistances of 3 Ω, 4Ω, 12Ω, and 16 Ω. The values of R1 and R2 (in ohms) are: A. 3, 4 B. 2, 12 C. 3, 16 D. 4, 12 E. 4, 16

4, 12

A total resistance of 3.0 Ω is to be produced by combining an unknown resistor R with a 12 Ω resistor. What is the value of R and how is it to be connected to the 12 Ω resistor? A. 4.0 Ω, parallel B. 4.0 Ω, series C. 2.4 Ω, parallel D. 2.4 Ω, series E. 9.0 Ω, series

4.0 Ω, parallel

Four 20-Ω resistors are connected in parallel and the combination is connected to a 20-V emf device. The current in the device is: A. 0.25A B. 1.0A C. 4.0A D. 5.0A E. 100A

4.0A

Two identical batteries, each with an emf of 18V and an internal resistance of 1 Ω, are wired in parallel by connecting their positive terminals together and connecting their negative terminals together. The combination is then wired across a 4-Ω resistor. The current in the 4-Ω resistor is: A. 1.0A B. 2.0A C. 4.0A D. 3.6A E. 7.2A

4.0A

Resistances of 2.0 Ω, 4.0 Ω, and 6.0 Ω and a 24-V emf device are all in series. The potential difference across the 2.0-Ω resistor is: A. 4V B. 8V C. 12V D. 24V E. 48V

4V

Four 20-Ω resistors are connected in series and the combination is connected to a 20-V emf device. The potential difference across any one of the resistors is: A. 1V B. 4V C. 5V D. 20V E. 80V

5V

A charged capacitor is being discharged through a resistor. At the end of one time constant the charge has been reduced by (1 − 1/e) = 63% of its initial value. At the end of two time constants the charge has been reduced by what percent of its initial value? A. 82% B. 86% C. 100% D. Between 90% and 100% E. Need to know more data to answer the question

86%

A certain voltmeter has an internal resistance of 10, 000 Ω and a range from 0 to 12V. To extend its range to 120V, use a series resistance of: A. 1, 111 Ω B. 90, 000 Ω C. 100, 000 Ω D. 108, 000 Ω E. 120, 000 Ω

90, 000 Ω

A certain voltmeter has an internal resistance of 10, 000 Ω and a range from 0 to 100V. To give it a range from 0 to 1000V, one should connect: A. 100, 000 Ω in series B. 100, 000 Ω in parallel C. 1000 Ω in series D. 1000 Ω in parallel E. 90, 000 Ω in series

90, 000 Ω in series

A certain galvanometer has a resistance of 100 Ω and requires 1mA for full scale deflection. To make this into a voltmeter reading 1V full scale, connect a resistance of: A. 1000 Ω in parallel B. 900 Ω in series C. 1000 Ω in series D. 10 Ω in parallel E. 0.1 Ω in series

900 Ω in series

If a circuit has L closed loops, B branches, and J junctions the number of independent loop equations is: A. B − J + 1 B. B − J C. B D. L E. L − J

B − J + 1

A resistor with resistance R1 and a resistor with resistance R2 are connected in parallel to an ideal battery with emf E. The rate of thermal energy generation in the resistor with resistance R1 is: A. E^2/R₁ B. E^2R₁/(R₁ + R₂)^2 C. E^2/(R₁ + R₂) D. E^2/R₂ E. E^2R₁/R²₂

E^2/R₁

A certain ammeter has an internal resistance of 1 Ω and a range from 0 to 50mA. To make its range from 0 to 5 A, use: A. a series resistance of 99 Ω B. an extremely large (say 106 Ω ) series resistance C. a resistance of 99 Ω in parallel D. a resistance of 1/99 Ω in parallel E. a resistance of 1/1000 Ω in parallel

a resistance of 1/99 Ω in parallel

An initially uncharged capacitor C is connected in series with resistor R. This combination is then connected to a battery of emf V₀₀. Sufficient time elapses so that a steady state is reached. Which of the following statements is NOT true? A. The time constant is independent of V₀ B. The final charge on C is independent of R C. The total thermal energy generated by R is independent of R D. The total thermal energy generated by R is independent of V₀ E. The initial current (just after the battery was connected) is independent of C

The total thermal energy generated by R is independent of R

To make a galvanometer into an ammeter, connect: A. a high resistance in parallel B. a high resistance in series C. a low resistance in series D. a low resistance in parallel E. a source of emf in series

a low resistance in parallel

"The sum of the currents into a junction equals the sum of the currents out of the junction" is a consequence of: A. Newton's third law B. Ohm's law C. Newton's second law D. conservation of energy E. conservation of charge

conservation of charge

"The sum of the emf's and potential differences around a closed loop equals zero" is a consequence of: A. Newton's third law B. Ohm's law C. Newton's second law D. conservation of energy E. conservation of charge

conservation of energy

Nine identical wires, each of diameter d and length L, are connected in series. The combination has the same resistance as a single similar wire of length L but whose diameter is: A. 3d B. 9d C. d/3 D. d/9 E. d/81

d/3

Resistor 1 has twice the resistance of resistor 2. The two are connected in parallel and a potential difference is maintained across the combination. The rate of thermal energy generation in 1 is: A. the same as that in 2 B. twice that in 2 C. half that in 2 D. four times that in 2 E. one-fourth that in 2

half that in 2

In the capacitor discharge formula q = q₀e^−t/RC the symbol t represents: A. the time constant B. the time it takes for C to lose the fraction 1/e of its initial charge C. the time it takes for C to lose the fraction (1 − 1/e) of its initial charge D. the time it takes for C to lose essentially all of its initial charge E. none of the above

none of the above

Two 110-V light bulbs, one "25W" and the other "100W", are connected in series to a 110V source. Then: A. the current in the 100-W bulb is greater than that in the 25-W bulb B. the current in the 100-W bulb is less than that in the 25-W bulb C. both bulbs will light with equal brightness D. each bulb will have a potential difference of 55V E. none of the above

none of the above

The time constant RC has units of: A. second/farad B. second/ohm C. 1/second D. second/watt E. none of these

none of these

The terminal potential difference of a battery is less than its emf: A. under all conditions B. only when the battery is being charged C. only when the battery is being discharged D. only when there is no current in the battery E. under no conditions

only when the battery is being discharged

The emf of a battery is equal to its terminal potential difference: A. under all conditions B. only when the battery is being charged C. only when a large current is in the battery D. only when there is no current in the battery E. under no conditions

only when there is no current in the battery

Two wires made of the same material have the same lengths but different diameters. They are connected in parallel to a battery. The quantity that is NOT the same for the wires is: A. the end-to-end potential difference B. the current C. the current density D. the electric field E. the electron drift velocity

the current

Two wires made of the same material have the same lengths but different diameters. They are connected in series to a battery. The quantity that is the same for the wires is: A. the end-to-end potential difference B. the current C. the current density D. the electric field E. the electron drift velocity

the current

The resistance of resistor 1 is twice the resistance of resistor 2. The two are connected in parallel and a potential difference is maintained across the combination. Then: A. the current in 1 is twice that in 2 B. the current in 1 is half that in 2 C. the potential difference across 1 is twice that across 2 D. the potential difference across 1 is half that across 2 E. none of the above are true

the current in 1 is half that in 2

A battery has an emf of 9V and an internal resistance of 2 Ω. If the potential difference across its terminals is greater than 9V: A. it must be connected across a large external resistance B. it must be connected across a small external resistance C. the current must be out of the positive terminal D. the current must be out of the negative terminal E. the current must be zero

the current must be out of the negative terminal

For any circuit the number of independent equations containing emf's, resistances, and currents equals: A. the number of junctions B. the number of junctions minus 1 C. the number of branches D. the number of branches minus 1 E. the number of closed loops

the number of branches

The resistance of resistor 1 is twice the resistance of resistor 2. The two are connected in series and a potential difference is maintained across the combination. Then: A. the current in 1 is twice that in 2 B. the current in 1 is half that in 2 C. the potential difference across 1 is twice that across 2 D. the potential difference across 1 is half that across 2 E. none of the above are true

the potential difference across 1 is twice that across 2

A battery is connected across a parallel combination of two identical resistors. If the potential difference across the terminals is V and the current in the battery is i, then: A. the potential difference across each resistor is V and the current in each resistor is i B. the potential difference across each resistor is V/2 and the current in each resistor is i/2 C. the potential difference across each resistor is V and the current in each resistor is i/2 D. the potential difference across each resistor is V/2 and the current in each resistor is i E. none of the above are true

the potential difference across each resistor is V and the current in each resistor is i/2

A battery is connected across a series combination of two identical resistors. If the potential difference across the terminals is V and the current in the battery is i, then: A. the potential difference across each resistor is V and the current in each resistor is i B. the potential difference across each resistor is V/2 and the current in each resistor is i/2 C. the potential difference across each resistor is V and the current in each resistor is i/2 D. the potential difference across each resistor is V/2 and the current in each resistor is i E. none of the above are true

the potential difference across each resistor is V/2 and the current in each resistor is i

A series circuit consists of a battery with internal resistance r and an external resistor R. If these two resistances are equal (r = R) then the thermal energy generated per unit time by the internal resistance r is: A. the same as by R B. half that by R C. twice that by R D. one-third that by R E. unknown unless the emf is given

the same as by R

Resistor 1 has twice the resistance of resistor 2. The two are connected in series and a potential difference is maintained across the combination. The rate of thermal energy generation in 1 is: A. the same as that in 2 B. twice that in 2 C. half that in 2 D. four times that in 2 E. one-fourth that in 2

twice that in 2

In the context of the loop and junctions rules for electrical circuits a junction is: A. where a wire is connected to a resistor B. where a wire is connected to a battery C. where only two wires are joined D. where three or more wires are joined E. where a wire is bent

where three or more wires are joined