Question 1

A resistor is made out of a long wire having a length L.Each end of the wire is attached to a terminal of a battery providing a constant voltage V0.A current I flows through the wire.If the wire were cut in half,making two wires of length L/2,and both wires were attached to the battery (the end of both wires attached to one terminal,and the other ends attached to the other terminal),what would be the total current flowing through the two wires?

Accepted Answer

A)  4I 
B)  2I 
C)  I 
D)  I/2 
E)  I/4

Question 2

For the circuit shown in the figure,the switch S is initially open and the capacitor is uncharged.The switch is then closed at time t = 0.How many seconds after closing the switch will the energy stored in the capacitor be equal to 50.2 mJ?

Accepted Answer

A)  81 s 
B)  65 s 
C)  97 s 
D)  110 s 
E)  130 s

Question 3

In the circuit shown in the figure,four identical resistors labeled A to D are connected to a battery as shown.S1 and S2 are switches.Which of the following actions would result in the GREATEST amount of current through resistor A?

Accepted Answer

A)  closing both switches 
B)  closing S1 only 
C)  closing S2 only 
D)  leaving both switches open as shown

Question 4

An uncharged 30.0-µF capacitor is connected in series with a 25.0-Ω resistor,a DC battery,and an open switch.The battery has an internal resistance of 10.0 Ω and the open-circuit voltage across its terminals is 50.0 V.The leads have no appreciable resistance.At time t = 0,the switch is suddenly closed.
(a)What is the maximum current through the 25.0-Ω resistor and when does it occur (immediately after closing the switch or after the switch has been closed for a long time)?
(b)What is the maximum charge that the capacitor receives?
(c)When the current in the circuit is 0.850 A,how much charge is on the plates of the capacitor?

Accepted Answer

The answer of An uncharged 30.0-µF capacitor is connected in...

Question 5

An uncharged 1.0-μF capacitor is connected in series with a  resistor,an ideal  battery,and an open switch.What is the voltage across the capacitor  after closing the switch?

Accepted Answer

A)  2.7 V 
B)  1.6 V 
C)  2.6 V 
D)  0.62 V

Question 6

In the circuit shown in the figure,all the lightbulbs are identical.Which of the following is the correct ranking of the brightness of the bulbs?

Accepted Answer

A)  B and C have equal brightness, and A is the dimmest. 
B)  A and B have equal brightness, and C is the dimmest. 
C)  A is brightest, C is dimmest, and B is in between. 
D)  A is the brightest, and B and C have equal brightness but less than A. 
E)  All three bulbs have the same brightness.

Question 7

For the circuit shown in the figure,the switch S is initially open and the capacitor voltage is 80 V.The switch is then closed at time t = 0.How long after closing the switch will the current in the resistor be 7.0 µA?

Accepted Answer

A)  87 s 
B)  95 s 
C)  78 s 
D)  69 s 
E)  61 s

Question 8

For the circuit shown in the figure,the current in the 8-Ω resistor is 0.50 A,and all quantities are accurate to 2 significant figures.What is the current in the 2-Ω resistor?

Accepted Answer

A)  2.25 A 
B)  0.75 A 
C)  4.5 A 
D)  9.5 A 
E)  6.4 A

Question 9

What is the maximum current that can be drawn from a 1.50-V battery with an internal resistance of 0.30 ohm?

Accepted Answer

A)  2.5 A 
B)  5.0 A 
C)  0.45 A 
D)  0.20 A 
E)  4.5 A

Question 10

Three resistors having resistances of 4.0 Ω,6.0 Ω,and 10.0 Ω are connected in parallel.If the combination is connected in series with an ideal 12-V battery and a 2.0-Ω resistor,what is the current through the 10.0-Ω resistor?

Accepted Answer

A)  0.59 A 
B)  2.7 A 
C)  6.4 A 
D)  11.2 A 
E)  16 A

Question 11

When a 100-Ω resistor is connected across the terminals of a battery of emf ε and internal resistance r,the battery delivers 0.794 W of power to the 100-Ω resistor.When the 100-Ω resistor is replaced by a 200-Ω resistor,the battery delivers 0.401 W of power to the 200-Ω resistor.What are the emf and internal resistance of the battery?

Accepted Answer

A)  ε = 10.0 V, r = 5.02 Ω 
B)  ε = 4.50 V, r = 4.00 Ω 
C)  ε = 9.00 V, r = 2.04 Ω 
D)  ε = 9.00 V, r = 1.01 Ω 
E)  ε = 12.0 V, r = 6.00 Ω

Question 12

A galvanometer has a coil with a resistance of 24.0 Ω,and a current of 180 μA causes it to deflect full scale.If this galvanometer is to be used to construct an ammeter that can read up to 10.0 A,what shunt resistor is required?

Accepted Answer

A)  123 µΩ 
B)  234 µΩ 
C)  342 µΩ 
D)  432 µΩ 
E)  423 µΩ

Question 13

As more resistors are added in parallel across a constant voltage source,the power supplied by the source

Accepted Answer

A)  increases. 
B)  decreases. 
C)  does not change.

Question 14

A multiloop circuit is shown in the figure.Some circuit quantities are not labeled.It is not necessary to solve the entire circuit.The current I1 is closest to

Accepted Answer

A)  zero. 
B)  +0.2 A. 
C)  +0.4 A. 
D)  -0.2 A. 
E)  -0.4 A.

Question 15

Thirteen resistors are connected across points A and B as shown in the figure.If all the resistors are accurate to 2 significant figures,what is the equivalent resistance between points A and B?

Accepted Answer

A)  4.0 Ω 
B)  6.0 Ω 
C)  8.0 Ω 
D)  10 Ω 
E)  12 Ω

Question 16

The figure shows three identical lightbulbs connected to a battery having a constant voltage across its terminals.What happens to the brightness of lightbulb 1 when the switch S is closed?

Accepted Answer

A)  The brightness will increase momentarily then return to its previous level. 
B)  The brightness increases permanently. 
C)  The brightness will decrease momentarily then return to its previous level. 
D)  The brightness remains the same as before the switch is closed. 
E)  The brightness decreases permanently.

Question 17

For the circuit shown in the figure,I = 0.50 A and R = 12 Ω.What is the value of the emf ε?

Accepted Answer

A)  18 V 
B)  24 V 
C)  6.0 V 
D)  12 V 
E)  48 V

Question 18

In the circuit shown in the figure,two 360.0-Ω resistors are connected in series with an ideal source of emf.A voltmeter with internal resistance of 6350 Ω is connected across one of the resistors and reads 3.23 V.Find the emf of the source.

Accepted Answer

The answer of In the circuit shown in the figure,two...

Question 19

For the circuit shown in the figure,determine the current in
(a)the 7.0-Ω resistor.
(b)the 8.0-Ω resistor.
(c)the 4.0-Ω resistor.

Accepted Answer

The answer of For the circuit shown in the figure,determine...

Question 20

A galvanometer G has an internal resistance rg.An AMMETER is constructed by incorporating the galvanometer and an additional resistance Rs.Which one of the figures below is the most appropriate circuit diagram for the ammeter?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Exam 26: Direct-Current Circuits