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Unit 2. Electricity and Magnetism
III. Electric circuits

Questions 1 - 3 refer to the image below
The RC circuit shown above, with the capacitor initially uncharged, is connected to a 120 V power source. The switch is closed at time t = 0, after which the current I in the ammeter, measured in amperes, is found to decay exponentially with respect to time (in seconds) according to I = (0.100).

1.What is the resistance of the resistor?
1200 Ω
200 Ω
120 Ω
20 Ω
10 Ω
2.What is the capacitance of the capacitor?
0.10 F
1.7 F
0.20 mF
1.7 μF
.20 μF
3.About how much time does it take for the current in the meter to drop to 0.014 A?
1 s
2 s
4 s
6 s
8 s
Questions 4 and 5 refer to the image below
An ammeter is inserted into the circuit shown above in order to determine the resistance of the unknown resistor. The terminal voltage of the battery is measured to be 12 V.

4.If the ammeter, considered to be ideal, reads 0.50 A, what is the resistance of the resistor?
3 Ω
6 Ω
12 Ω
24 Ω
48 Ω
5.If the small internal resistance of the ammeter is taken into account, how does the resistance of the unknown resistor compare to the value calculated in question 4?
Its resistance is exactly equal to the value calculated in question 4.
Its resistance is slightly greater than the value calculated in question 4.
Its resistance is slightly less than the value calculated in question 4.
Its resistance depends on the resistance of the known resistor.
Its resistance depends on the internal resistance of the battery.
6.Three identical bulbs, all of resistance R, are attached to a battery as shown above. What happens to the brightness of bulb A when the switch is closed?
It gets brighter.
It gets dimmer.
Its brightness is unchanged.
Whether the bulb gets brighter or dimmer depends on the value of R.
Whether the bulb gets brighter or dimmer depends on both the value of R and the EMF of the battery.
7.An engineer needs to use a 2.0 nF capacitor in a circuit, but she only has 1.0, 3.0, and 5.0 nF capacitors available in the storage cabinet. Which of the following diagrams shows how the available capacitors can be connected in order to satisfy the engineer's need?

A
B
C
D
8.The combination of capacitors shown above has completely charged by connection to a 6 V battery. What is the voltage across the 2 μF capacitor?
1 V
2 V
3 V
4 V
6 V
9.A light bulb, assumed to obey ohm's law, dissipates 100 W when connected to a 100 V power supply. This same bulb is instead plugged into a 200 V wall outlet. What power does the bulb now dissipate?
50 W
25 W
100 W
400 W
200 W
10.A fully charged capacitor is discharged through two parallel resistors. Which of the following must be the same for both resistors?
The current through each at any time during the discharge
The voltage across each at any time during the discharge
The total charge conducted through each during the discharge
The resistance of each
The resistivity of each