Question 1

The circuit below contains 4 100-W light bulbs. The emf is 110 V. Which light bulb(s) is(are) brightest?

Accepted Answer

A) A 
B) B 
C) C 
D) D 
E) C and D 
A) A 
B) B 
C) C 
D) D 
E) C and D

Question 2

If R1 = 10 Ω, R2 = 15 Ω, R3 = 20 Ω, and I = 0.50 A, at what rate is heat being generated in these resistors?

Accepted Answer

A) 29 W 
B) 16 W 
C) 22 W 
D) 11 W 
E) 1.1 W 
A) 29 W 
B) 16 W 
C) 22 W 
D) 11 W 
E) 1.1 W

Question 3

What is the current in the 15-Ω resistor when ε = 9.0 V?

Accepted Answer

A) 0.20 A 
B) 0.30 A 
C) 0.10 A 
D) 0.26 A 
E) 0.60 A 
A) 0.20 A 
B) 0.30 A 
C) 0.10 A 
D) 0.26 A 
E) 0.60 A

Question 4

The circuit below shows three resistors in parallel. R3 > R2 > R1. The resistors are all made of the same wire with the same diameter but have different lengths. Rank the magnitudes of the electric fields in the resistors from least to greatest.

Accepted Answer

A) E3 < E2 < E1. 
B) E2 < E1 = E3. 
C) E1 = E2 = E3. 
D) E1 = E3 < E2. 
E) E1 < E2 < E3. 
A) E3 < E2 < E1. 
B) E2 < E1 = E3. 
C) E1 = E2 = E3. 
D) E1 = E3 < E2. 
E) E1 < E2 < E3.

Question 5

The diagram shown represents a portion of a wire in a circuit. A current is flowing in the wire in the direction shown. Under the convention that it is positive charge that flows the electric field points in the direction of the current. How can the electric field change direction where the wire bends?

Accepted Answer

A) There is an excess of negative charge in the center of the wire. 
B) There is an excess of positive charge at the bottom end of the wire. 
C) There is an excess of negative charge at the right end of the upper portion of the wire. 
D) There is an accumulation of positive charge on the surface, particularly at the bend, such that the sum of electric fields gives the new electric field. 
E) There is an accumulation of electrical potential as the current traverses the wire: The higher potential in the lower half is the source of the field. 
A) There is an excess of negative charge in the center of the wire. 
B) There is an excess of positive charge at the bottom end of the wire. 
C) There is an excess of negative charge at the right end of the upper portion of the wire. 
D) There is an accumulation of positive charge on the surface, particularly at the bend, such that the sum of electric fields gives the new electric field. 
E) There is an accumulation of electrical potential as the current traverses the wire: The higher potential in the lower half is the source of the field.

Question 6

In an RC circuit, how many time constants must elapse if an initially uncharged capacitor is to reach 80% of its final potential difference?

Accepted Answer

A) 2.2 
B) 1.9 
C) 1.6 
D) 3.0 
E) 5.0 
A) 2.2 
B) 1.9 
C) 1.6 
D) 3.0 
E) 5.0

Question 7

If the current in the 4.0-Ω resistor is 1.4 A, what is the magnitude of the potential difference, VA − VB?

Accepted Answer

A) 69 V 
B) 55 V 
C) 62 V 
D) 48 V 
E) 31 V 
A) 69 V 
B) 55 V 
C) 62 V 
D) 48 V 
E) 31 V

Question 8

Determine the magnitude and sense (direction) of the current in the 10-Ω resistor when I = 1.8 A.

Accepted Answer

A) 1.6 A right to left 
B) 1.6 A left to right 
C) 1.2 A right to left 
D) 1.2 A left to right 
E) 1.8 A left to right 
A) 1.6 A right to left 
B) 1.6 A left to right 
C) 1.2 A right to left 
D) 1.2 A left to right 
E) 1.8 A left to right

Question 9

If Q = 400 μC and the potential difference VA − VB = −10 V in the circuit segment shown below, what is the current in the resistor?

Accepted Answer

A) 1.0 mA right to left 
B) 1.0 mA left to right 
C) 3.5 mA right to left 
D) 3.5 mA left to right 
E) None of the above 
A) 1.0 mA right to left 
B) 1.0 mA left to right 
C) 3.5 mA right to left 
D) 3.5 mA left to right 
E) None of the above

Question 10

What is the current in the 10-Ω resistor? ​   ​

Accepted Answer

A) 0.60 A 
B) 3.0 A 
C) 1.2 A 
D) 2.4 A 
E) 0.30 A 
A) 0.60 A 
B) 3.0 A 
C) 1.2 A 
D) 2.4 A 
E) 0.30 A

Question 11

If R1 = 3.0 Ω, R2 = 6.0 Ω, R3 = 12 Ω, and I = 0.50 A, at what rate is heat being generated in R1?

Accepted Answer

A) 20 W 
B) 17 W 
C) 12 W 
D) 31 W 
E) 6.0 W 
A) 20 W 
B) 17 W 
C) 12 W 
D) 31 W 
E) 6.0 W

Question 12

Which of the identical light bulb(s) is(are) brightest when the capacitor has half its maximum charge?

Accepted Answer

A) A 
B) B 
C) C 
D) A and B 
E) All three are equally bright. 
A) A 
B) B 
C) C 
D) A and B 
E) All three are equally bright.

Question 13

The circuit below contains 4 100-W light bulbs. The emf is 110 V. Which light bulb(s) is(are) brightest?

Accepted Answer

A) A 
B) B 
C) C 
D) D 
E) C and D 
A) A 
B) B 
C) C 
D) D 
E) C and D

Question 14

When a capacitor is fully charged, the current through the capacitor in a direct-current circuit is

Accepted Answer

A) zero. 
B) at its maximum value. 
C) equal to the current in a resistive circuit in parallel with the capacitor circuit. 
D) greater than the current in a resistor that is farther from the battery than the capacitor. 
E) zero if it is the only capacitor, but maximum if there is another capacitor in series with it. 
A) zero. 
B) at its maximum value. 
C) equal to the current in a resistive circuit in parallel with the capacitor circuit. 
D) greater than the current in a resistor that is farther from the battery than the capacitor. 
E) zero if it is the only capacitor, but maximum if there is another capacitor in series with it.

Question 15

At what rate is thermal energy generated in the 30-Ω resistor?

Accepted Answer

A) 20 W 
B) 27 W 
C) 60 W 
D) 13 W 
E) 30 W 
A) 20 W 
B) 27 W 
C) 60 W 
D) 13 W 
E) 30 W

Question 16

At what rate is thermal energy being generated in the 2R-resistor when ε = 12 V and R = 3.0 Ω?

Accepted Answer

A) 12 W 
B) 24 W 
C) 6.0 W 
D) 3.0 W 
E) 1.5 W 
A) 12 W 
B) 24 W 
C) 6.0 W 
D) 3.0 W 
E) 1.5 W

Question 17

How long will it take a charged 80-μF capacitor to lose 20% of its initial energy when it is allowed to discharge through a 45-Ω resistor?

Accepted Answer

A) 0.92 ms 
B) 0.64 ms 
C) 0.40 ms 
D) 0.19 ms 
E) 0.80 ms 
A) 0.92 ms 
B) 0.64 ms 
C) 0.40 ms 
D) 0.19 ms 
E) 0.80 ms

Question 18

The circuit below contains three 100-watt light bulbs and a capacitor. The emf ε = 110V. The capacitor is fully charged. Which light bulb(s) is(are) dimmest?

Accepted Answer

A) A 
B) B 
C) C 
D) A and B 
E) All three are equally bright (or dim). 
A) A 
B) B 
C) C 
D) A and B 
E) All three are equally bright (or dim).

Question 19

How much heat is produced in the 10-Ω resistor in 5.0 s when ε = 18 V?

Accepted Answer

A) 72 J 
B) 32 J 
C) 50 J 
D) 18 J 
E) 90 J 
A) 72 J 
B) 32 J 
C) 50 J 
D) 18 J 
E) 90 J

Question 20

Determine ε when I = 0.50 A and R = 12 Ω.

Accepted Answer

A) 12 V 
B) 24 V 
C) 30 V 
D) 15 V 
E) 6.0 V 
A) 12 V 
B) 24 V 
C) 30 V 
D) 15 V 
E) 6.0 V

Exam 29: Direct Current Dc Circuits

The circuit below contains 4 100-W light bulbs. The emf is 110 V. Which light bulb(s) is(are) brightest?

If R1 = 10 Ω, R2 = 15 Ω, R3 = 20 Ω, and I = 0.50 A, at what rate is heat being generated in these resistors?

What is the current in the 15-Ω resistor when ε = 9.0 V?

The circuit below shows three resistors in parallel. R3 > R2 > R1. The resistors are all made of the same wire with the same diameter but have different lengths. Rank the magnitudes of the electric fields in the resistors from least to greatest.

In an RC circuit, how many time constants must elapse if an initially uncharged capacitor is to reach 80% of its final potential difference?

If the current in the 4.0-Ω resistor is 1.4 A, what is the magnitude of the potential difference, VA − VB?

Determine the magnitude and sense (direction) of the current in the 10-Ω resistor when I = 1.8 A.

If Q = 400 μC and the potential difference VA − VB = −10 V in the circuit segment shown below, what is the current in the resistor?

What is the current in the 10-Ω resistor? ​ ​

If R1 = 3.0 Ω, R2 = 6.0 Ω, R3 = 12 Ω, and I = 0.50 A, at what rate is heat being generated in R1?

Which of the identical light bulb(s) is(are) brightest when the capacitor has half its maximum charge?

The circuit below contains 4 100-W light bulbs. The emf is 110 V. Which light bulb(s) is(are) brightest?

When a capacitor is fully charged, the current through the capacitor in a direct-current circuit is

At what rate is thermal energy generated in the 30-Ω resistor?

At what rate is thermal energy being generated in the 2R-resistor when ε = 12 V and R = 3.0 Ω?

How long will it take a charged 80-μF capacitor to lose 20% of its initial energy when it is allowed to discharge through a 45-Ω resistor?

The circuit below contains three 100-watt light bulbs and a capacitor. The emf ε = 110V. The capacitor is fully charged. Which light bulb(s) is(are) dimmest?

How much heat is produced in the 10-Ω resistor in 5.0 s when ε = 18 V?

Determine ε when I = 0.50 A and R = 12 Ω.

Getting Started

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What is the current in the 10-Ω resistor?