Question 1

Four 20. Ω resistors are connected in parallel. What is the equivalent resistance?

Accepted Answer

The answer of Four 20. Ω resistors are connected in...

Question 2

Given 3 capacitors:
 4.00 μF, 7.00 μF, and 9.00 μF; what is the equivalent capacity if they are connected in parallel?

Accepted Answer

The answer of Given 3 capacitors:
 4.00 μF, 7.00 μF,...

Question 3

Which one of the following is a correct statement for a number of resistors connected in series or parallel?

Accepted Answer

A)  The total resistance in a series circuit decreases as more resistors are added. 
B)  The flow of current is different through resistors connected in a series circuit. 
C)  The voltage is different across resistors connected in a parallel circuit. 
D)  The total resistance in a parallel circuit decreases as more resistors are added. 
E)  None of the above statements is correct. 
A)  The total resistance in a series circuit decreases as more resistors are added. 
B)  The flow of current is different through resistors connected in a series circuit. 
C)  The voltage is different across resistors connected in a parallel circuit. 
D)  The total resistance in a parallel circuit decreases as more resistors are added. 
E)  None of the above statements is correct.

Question 4

The length of a certain wire is kept same while its radius is doubled. What is the change in the resistance of this wire?

Accepted Answer

A)  It is doubled. 
B)  It is quadrupled. 
C)  It is reduced by a factor of 2. 
D)  It is reduced by a factor of 4. 
E)  It is reduced by a factor of 8. 
A)  It is doubled. 
B)  It is quadrupled. 
C)  It is reduced by a factor of 2. 
D)  It is reduced by a factor of 4. 
E)  It is reduced by a factor of 8.

Question 5

FIGURE 21-18  
-A system of capacitors is connected across a 90 V DC voltage source as shown in Figure 21-18. What is the equivalent capacitance of this system?

Accepted Answer

A)  1.5 μF 
B)  15 μF 
C)  3.6 μF 
D)  3.3 μF 
E)  None of the other answers is correct. 
A)  1.5 μF 
B)  15 μF 
C)  3.6 μF 
D)  3.3 μF 
E)  None of the other answers is correct.

Question 6

FIGURE 21-8  
-Five equal resistors, of value 2.0 Ω each, are connected as shown in Figure 21-8. What is the equivalent resistance of this circuit?

Accepted Answer

A)  1.0 Ω 
B)  10.0 Ω 
C)  2.0 Ω 
D)  6.0 Ω 
E)  0.40 Ω 
A)  1.0 Ω 
B)  10.0 Ω 
C)  2.0 Ω 
D)  6.0 Ω 
E)  0.40 Ω

Question 7

Two resistors in series equal 9.0 ohms total; but the same two resistors in parallel are equivalent to 2.0 ohms. What are the resistor values?

Accepted Answer

The answer of Two resistors in series equal 9.0 ohms...

Question 8

An RC circuit is connected across a DC voltage source through an open switch. The switch is closed at t = 0 s. Which of the following is a correct statement regarding this circuit?

Accepted Answer

A)  The charge on the capacitor after four time constants is about 98% of the maximum value. 
B)  The charge on the capacitor after one time constant is about 25% of its maximum value. 
C)  The charge on the capacitor after one time constant is about 50% of its maximum value. 
D)  The voltage on the capacitor after two time constants is about 14% of the maximum value. 
E)  The voltage on this capacitor after two time constants is about 100% of its maximum value. 
A)  The charge on the capacitor after four time constants is about 98% of the maximum value. 
B)  The charge on the capacitor after one time constant is about 25% of its maximum value. 
C)  The charge on the capacitor after one time constant is about 50% of its maximum value. 
D)  The voltage on the capacitor after two time constants is about 14% of the maximum value. 
E)  The voltage on this capacitor after two time constants is about 100% of its maximum value.

Question 9

Conventional current is the flow of positive charge from higher to lower potential.

Accepted Answer

A) True 
 B)False

Question 10

A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in series to the first, the time constant of the new RC circuit will be

Accepted Answer

A)  the same as before. 
B)  larger than before. 
C)  smaller than before. 
D)  variable. 
A)  the same as before. 
B)  larger than before. 
C)  smaller than before. 
D)  variable.

Question 11

What charge appears on the plates of a 2.00 μF capacitor when it is charged to

Accepted Answer

The answer of What charge appears on the plates of...

Question 12

FIGURE 21-19  
-Four capacitors are connected as shown in Figure 21-19. What is the charge on a 2.0-μF capacitor?

Accepted Answer

A)  68 μC 
B)  90 μC 
C)  240 μC 
D)  120 μC 
E)  180 μC 
A)  68 μC 
B)  90 μC 
C)  240 μC 
D)  120 μC 
E)  180 μC

Question 13

Four resistors of 20 Ω, 40 Ω, 60 Ω, and 80 Ω are connected across a 50-V DC source. What is the current through this circuit?

Accepted Answer

A)  0.25 A 
B)  0.50 A 
C)  0.75 A 
D)  2.0 A 
E)  4.0 A 
A)  0.25 A 
B)  0.50 A 
C)  0.75 A 
D)  2.0 A 
E)  4.0 A

Question 14

FIGURE 21-2  
-Which of the following equations represents a Kirchhoff's voltage rule for the circuit shown in Figure 21-2?

Accepted Answer

A)  -6 V + 2 V - (6Ω)i3 = 0 V 
B)  +4 V - (8Ω) i2 - (12Ω) i1 = 0 V 
C)  -(8Ω) i2 + 4 V + 6 V + (12Ω) i1 = 0 V 
D)  +6 V - (12Ω) i1 - (8Ω) i2 + 4 V = 0 V 
E)  none of the above 
A)  -6 V + 2 V - (6Ω)i3 = 0 V 
B)  +4 V - (8Ω) i2 - (12Ω) i1 = 0 V 
C)  -(8Ω) i2 + 4 V + 6 V + (12Ω) i1 = 0 V 
D)  +6 V - (12Ω) i1 - (8Ω) i2 + 4 V = 0 V 
E)  none of the above

Question 15

FIGURE 21-9  
-A 4.0-Ω resistor is connected in parallel with a 12-Ω resistor and both of these are connected to a DC power supply with voltage V as shown in Figure 21-9. If the total current in this circuit is 2.0 A, what is the current through the 4.0-Ω resistor?

Accepted Answer

A)  2.0 A 
B)  2.5 A 
C)  0.5 A 
D)  3.0 A 
E)  1.5 A 
A)  2.0 A 
B)  2.5 A 
C)  0.5 A 
D)  3.0 A 
E)  1.5 A

Question 16

If the internal resistance of my 1.5 volt battery is 0.50 ohms, what is the maximum possible power and current that can be delivered from it?

Accepted Answer

4.5 watts

Question 17

Four equal resistors connected in series have same current and same voltage across each resistor.

Accepted Answer

A) True 
 B)False

Question 18

The resistance of a superconductor is infinite once it goes into the superconductivity state.

Accepted Answer

A) True 
 B)False

Question 19

Given 3 capacitors:
 4.00 μF, 7.00 μF, and 9.00 μF; what is the equivalent capacity if they are connected in series?

Accepted Answer

The answer of Given 3 capacitors:
 4.00 μF, 7.00 μF,...

Question 20

FIGURE 21-6  
-Three resistors of values 2 Ω, 6 Ω and 12 Ω are connected across a 2.0-V DC voltage source as shown in Figure 21-6. What is the total current I flowing this circuit?

Accepted Answer

A)  0.70 A 
B)  1.5 A 
C)  2.0 A 
D)  3.0 A 
E)  6.0 A 
A)  0.70 A 
B)  1.5 A 
C)  2.0 A 
D)  3.0 A 
E)  6.0 A

Exam 21: Electric Current and Direct-Current Circuits

Four 20. Ω resistors are connected in parallel. What is the equivalent resistance?

Given 3 capacitors: 4.00 μF, 7.00 μF, and 9.00 μF; what is the equivalent capacity if they are connected in parallel?

Which one of the following is a correct statement for a number of resistors connected in series or parallel?

The length of a certain wire is kept same while its radius is doubled. What is the change in the resistance of this wire?

FIGURE 21-18 -A system of capacitors is connected across a 90 V DC voltage source as shown in Figure 21-18. What is the equivalent capacitance of this system?

FIGURE 21-8 -Five equal resistors, of value 2.0 Ω each, are connected as shown in Figure 21-8. What is the equivalent resistance of this circuit?

Two resistors in series equal 9.0 ohms total; but the same two resistors in parallel are equivalent to 2.0 ohms. What are the resistor values?

An RC circuit is connected across a DC voltage source through an open switch. The switch is closed at t = 0 s. Which of the following is a correct statement regarding this circuit?

Conventional current is the flow of positive charge from higher to lower potential.

A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in series to the first, the time constant of the new RC circuit will be

What charge appears on the plates of a 2.00 μF capacitor when it is charged to

FIGURE 21-19 -Four capacitors are connected as shown in Figure 21-19. What is the charge on a 2.0-μF capacitor?

Four resistors of 20 Ω, 40 Ω, 60 Ω, and 80 Ω are connected across a 50-V DC source. What is the current through this circuit?

FIGURE 21-2 -Which of the following equations represents a Kirchhoff's voltage rule for the circuit shown in Figure 21-2?

FIGURE 21-9 -A 4.0-Ω resistor is connected in parallel with a 12-Ω resistor and both of these are connected to a DC power supply with voltage V as shown in Figure 21-9. If the total current in this circuit is 2.0 A, what is the current through the 4.0-Ω resistor?

If the internal resistance of my 1.5 volt battery is 0.50 ohms, what is the maximum possible power and current that can be delivered from it?

Four equal resistors connected in series have same current and same voltage across each resistor.

The resistance of a superconductor is infinite once it goes into the superconductivity state.

Given 3 capacitors: 4.00 μF, 7.00 μF, and 9.00 μF; what is the equivalent capacity if they are connected in series?

FIGURE 21-6 -Three resistors of values 2 Ω, 6 Ω and 12 Ω are connected across a 2.0-V DC voltage source as shown in Figure 21-6. What is the total current I flowing this circuit?

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