Question 1

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

Question 2

An initially uncharged 10-μF capacitor is charged by a 10-V battery through a resistance R. The capacitor reaches a potential difference of 4 V in a period of 3 s after the charging began. Find the value of R.

Accepted Answer

The answer of An initially uncharged 10-μF capacitor is charged...

Question 3

The capacitors are completely discharged in the circuit shown below.   The two resistors have the same resistance R and the two capacitors have the same capacitance C. After the switch is closed, the current

Accepted Answer

A)  is greatest in C1. 
B)  is greatest in C2. 
C)  is greatest in R1. 
D)  is greatest in R2. 
E)  is the same in C1, C2, R1 and R2. 
A)  is greatest in C1. 
B)  is greatest in C2. 
C)  is greatest in R1. 
D)  is greatest in R2. 
E)  is the same in C1, C2, R1 and R2.

Question 4

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 5

At t = 0 the switch S is closed with the capacitor uncharged. If C = 40 μF, ε = 50 V, and R = 5.0 kΩ, how much energy is stored by the capacitor when I = 2.0 mA?

Accepted Answer

A)  20 mJ 
B)  28 mJ 
C)  32 mJ 
D)  36 mJ 
E)  40 mJ 
A)  20 mJ 
B)  28 mJ 
C)  32 mJ 
D)  36 mJ 
E)  40 mJ

Question 6

What is the potential difference VB − VA when the I = 1.5 A in the circuit segment below?

Accepted Answer

A)  +22 V 
B)  −22 V 
C)  −38 V 
D)  +38 V 
E)  +2.0 V 
A)  +22 V 
B)  −22 V 
C)  −38 V 
D)  +38 V 
E)  +2.0 V

Question 7

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

Accepted Answer

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

Question 8

A circuit consists of N resistors, all of resistance R, connected as shown below. A potential difference V is applied to the circuit. The equivalent resistance of the circuit is

Accepted Answer

A) 
  . 
B)  R. 
C) 
  . 
D)  NR. 
E)  4NR. 
A) 
  . 
B)  R. 
C) 
  . 
D)  NR. 
E)  4NR.

Question 9

What is the equivalent resistance between points A and B in the figure when R = 20 Ω?

Accepted Answer

A)  77 Ω 
B)  63 Ω 
C)  70 Ω 
D)  84 Ω 
E)  140 Ω 
A)  77 Ω 
B)  63 Ω 
C)  70 Ω 
D)  84 Ω 
E)  140 Ω

Question 10

In an RC circuit, what fraction of the final energy is stored in an initially uncharged capacitor after it has been charging for 3.0 time constants?

Accepted Answer

A)  0.84 
B)  0.90 
C)  0.75 
D)  0.60 
E)  0.03 
A)  0.84 
B)  0.90 
C)  0.75 
D)  0.60 
E)  0.03

Question 11

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 12

At t = 0 the switch S is closed with the capacitor uncharged. If C = 30 μF, ε = 50 V, and R = 10 kΩ, what is the potential difference across the capacitor when I = 2.0 mA?

Accepted Answer

A)  20 V 
B)  15 V 
C)  25 V 
D)  30 V 
E)  45 V 
A)  20 V 
B)  15 V 
C)  25 V 
D)  30 V 
E)  45 V

Question 13

If ε = 8.0 V, at what rate is that emf providing energy to the circuit shown below?

Accepted Answer

A)  8.4 W 
B)  7.6 W 
C)  5.6 W 
D)  11 W 
E)  2.0 W 
A)  8.4 W 
B)  7.6 W 
C)  5.6 W 
D)  11 W 
E)  2.0 W

Question 14

At t = 0 the switch S is closed with the capacitor uncharged. If C = 30 μF, ε = 30 V, and R = 5.0 kΩ, at what rate is energy being stored in the capacitor when I = 2.0 mA?

Accepted Answer

A)  32 mW 
B)  40 mW 
C)  44 mW 
D)  36 mW 
E)  80 mW 
A)  32 mW 
B)  40 mW 
C)  44 mW 
D)  36 mW 
E)  80 mW

Question 15

The circuit below contains three 100-watt light bulbs. The emf ε = 110 V. Which light bulb(s) is(are) the brightest?

Accepted Answer

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

Question 16

A certain brand of hot dog cooker applies a potential difference (120 V) to opposite ends of the hot dog and cooks by means of the joule heat produced. If 60 kJ is needed to cook each hot dog, what current is needed to cook four hot dogs simultaneously in 3.0 min?

Accepted Answer

A)  11 A 
B)  2.8 A 
C)  8.3 A 
D)  2.1 A 
E)  3.6 A 
A)  11 A 
B)  2.8 A 
C)  8.3 A 
D)  2.1 A 
E)  3.6 A

Question 17

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 18

The circuit below contains three 100-W light bulbs and a capacitor. The emf is 110 V and the capacitor is fully charged. Which light bulb(s) is(are) brightest?

Accepted Answer

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

Question 19

What is the equivalent resistance between points a and b when R = 13 Ω?

Accepted Answer

A)  29 Ω 
B)  23 Ω 
C)  26 Ω 
D)  20 Ω 
E)  4.6 Ω 
A)  29 Ω 
B)  23 Ω 
C)  26 Ω 
D)  20 Ω 
E)  4.6 Ω

Question 20

At what rate is thermal energy generated in the 20-Ω resistor when ε = 20 V?

Accepted Answer

A)  6.5 W 
B)  1.6 W 
C)  15 W 
D)  26 W 
E)  5.7 W 
A)  6.5 W 
B)  1.6 W 
C)  15 W 
D)  26 W 
E)  5.7 W

Exam 28: Direct-Current Circuits

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

An initially uncharged 10-μF capacitor is charged by a 10-V battery through a resistance R. The capacitor reaches a potential difference of 4 V in a period of 3 s after the charging began. Find the value of R.

The capacitors are completely discharged in the circuit shown below. The two resistors have the same resistance R and the two capacitors have the same capacitance C. After the switch is closed, the current

At t = 0 the switch S is closed with the capacitor uncharged. If C = 40 μF, ε = 50 V, and R = 5.0 kΩ, how much energy is stored by the capacitor when I = 2.0 mA?

What is the potential difference VB − VA when the I = 1.5 A in the circuit segment below?

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

A circuit consists of N resistors, all of resistance R, connected as shown below. A potential difference V is applied to the circuit. The equivalent resistance of the circuit is

What is the equivalent resistance between points A and B in the figure when R = 20 Ω?

In an RC circuit, what fraction of the final energy is stored in an initially uncharged capacitor after it has been charging for 3.0 time constants?

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

At t = 0 the switch S is closed with the capacitor uncharged. If C = 30 μF, ε = 50 V, and R = 10 kΩ, what is the potential difference across the capacitor when I = 2.0 mA?

If ε = 8.0 V, at what rate is that emf providing energy to the circuit shown below?

At t = 0 the switch S is closed with the capacitor uncharged. If C = 30 μF, ε = 30 V, and R = 5.0 kΩ, at what rate is energy being stored in the capacitor when I = 2.0 mA?

The circuit below contains three 100-watt light bulbs. The emf ε = 110 V. Which light bulb(s) is(are) the brightest?

A certain brand of hot dog cooker applies a potential difference (120 V) to opposite ends of the hot dog and cooks by means of the joule heat produced. If 60 kJ is needed to cook each hot dog, what current is needed to cook four hot dogs simultaneously in 3.0 min?

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

The circuit below contains three 100-W light bulbs and a capacitor. The emf is 110 V and the capacitor is fully charged. Which light bulb(s) is(are) brightest?

What is the equivalent resistance between points a and b when R = 13 Ω?

At what rate is thermal energy generated in the 20-Ω resistor when ε = 20 V?

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What is the potential difference V_B − V_A when the I = 1.5 A in the circuit segment below?