Electric Circuits Multiple-Choice Practice Questions | AP Physics C Electricity and Magnetism - Grade 9 PDF Download

 Page 1


Section I: Multiple Choice
1. A wire made of brass and a wire made of silver have the same length, but the diameter of the
brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater
than the resistivity of silver. If R
B
 denotes the resistance of the brass wire and R
S
 denotes the
resistance of the silver wire, which of the following is true?
(A) R
B
 = R
S
(B) R
B
 = R
S
(C) R
B
 = R
S
(D) R
B
 = R
S
(E) R
B
 = R
S
2. For an ohmic conductor, doubling the voltage without changing the resistance will cause the
current to
(A) decrease by a factor of 4
(B) decrease by a factor of 2
(C) remain unchanged
(D) increase by a factor of 2
(E) increase by a factor of 4
3. A given circuit uses 125 watts of power. If the circuit has a total resistance of 5 O, at what
voltage must it be operating?
(A)    5 V
(B)  15 V
(C)  25 V
(D)  45 V
(E) 625 V
4. An ammeter is a device than can be arranged in a circuit to measure the current through
flowing through a particular part of the circuit. Which of the following sets of characteristics
should it possess?
(A) It should have high resistance and should be arranged in series with the part being
measured.
(B) It should have low resistance and should be arranged in series with the part being
measured.
(C) It should have high resistance and should be arranged in parallel with the part being
measured.
(D) It should have low resistance and should be arranged in parallel with the part being
measured.
(E) It should have the same resistance as the part being measured and should be arranged in
series with the part being measured.
Page 2


Section I: Multiple Choice
1. A wire made of brass and a wire made of silver have the same length, but the diameter of the
brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater
than the resistivity of silver. If R
B
 denotes the resistance of the brass wire and R
S
 denotes the
resistance of the silver wire, which of the following is true?
(A) R
B
 = R
S
(B) R
B
 = R
S
(C) R
B
 = R
S
(D) R
B
 = R
S
(E) R
B
 = R
S
2. For an ohmic conductor, doubling the voltage without changing the resistance will cause the
current to
(A) decrease by a factor of 4
(B) decrease by a factor of 2
(C) remain unchanged
(D) increase by a factor of 2
(E) increase by a factor of 4
3. A given circuit uses 125 watts of power. If the circuit has a total resistance of 5 O, at what
voltage must it be operating?
(A)    5 V
(B)  15 V
(C)  25 V
(D)  45 V
(E) 625 V
4. An ammeter is a device than can be arranged in a circuit to measure the current through
flowing through a particular part of the circuit. Which of the following sets of characteristics
should it possess?
(A) It should have high resistance and should be arranged in series with the part being
measured.
(B) It should have low resistance and should be arranged in series with the part being
measured.
(C) It should have high resistance and should be arranged in parallel with the part being
measured.
(D) It should have low resistance and should be arranged in parallel with the part being
measured.
(E) It should have the same resistance as the part being measured and should be arranged in
series with the part being measured.
5. Determine the equivalent resistance between points a and b in the figure above.
(A) 0.167 O
(B) 0.25 O
(C) 0.333 O
(D) 1.5 O
(E) 2 O
6. Three identical light bulbs are connected to a source of emf, as shown in the diagram above.
What will happen if the middle bulb burns out?
(A) All the bulbs will go out.
(B) The light intensity of the other two bulbs will decrease (but they won’t go out).
(C) The light intensity of the other two bulbs will increase.
(D) The light intensity of the other two bulbs will remain the same.
(E) More current will be drawn from the source of emf.
7. Two identical circuits are created, each with an ideal battery. The circuits each have a
capacitor. The capacitors are allowed to fully charge. At this point, both capacitors are fitted
with dielectrics, however one circuit has the ideal battery removed at the same time. The other
circuit keeps its battery. After some time has elapsed, which of the following values would be
the same in both capacitors?
(A) Potential energy
(B) Charge
(C) Capacitance
(D) Voltage
(E) Electric field
Page 3


Section I: Multiple Choice
1. A wire made of brass and a wire made of silver have the same length, but the diameter of the
brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater
than the resistivity of silver. If R
B
 denotes the resistance of the brass wire and R
S
 denotes the
resistance of the silver wire, which of the following is true?
(A) R
B
 = R
S
(B) R
B
 = R
S
(C) R
B
 = R
S
(D) R
B
 = R
S
(E) R
B
 = R
S
2. For an ohmic conductor, doubling the voltage without changing the resistance will cause the
current to
(A) decrease by a factor of 4
(B) decrease by a factor of 2
(C) remain unchanged
(D) increase by a factor of 2
(E) increase by a factor of 4
3. A given circuit uses 125 watts of power. If the circuit has a total resistance of 5 O, at what
voltage must it be operating?
(A)    5 V
(B)  15 V
(C)  25 V
(D)  45 V
(E) 625 V
4. An ammeter is a device than can be arranged in a circuit to measure the current through
flowing through a particular part of the circuit. Which of the following sets of characteristics
should it possess?
(A) It should have high resistance and should be arranged in series with the part being
measured.
(B) It should have low resistance and should be arranged in series with the part being
measured.
(C) It should have high resistance and should be arranged in parallel with the part being
measured.
(D) It should have low resistance and should be arranged in parallel with the part being
measured.
(E) It should have the same resistance as the part being measured and should be arranged in
series with the part being measured.
5. Determine the equivalent resistance between points a and b in the figure above.
(A) 0.167 O
(B) 0.25 O
(C) 0.333 O
(D) 1.5 O
(E) 2 O
6. Three identical light bulbs are connected to a source of emf, as shown in the diagram above.
What will happen if the middle bulb burns out?
(A) All the bulbs will go out.
(B) The light intensity of the other two bulbs will decrease (but they won’t go out).
(C) The light intensity of the other two bulbs will increase.
(D) The light intensity of the other two bulbs will remain the same.
(E) More current will be drawn from the source of emf.
7. Two identical circuits are created, each with an ideal battery. The circuits each have a
capacitor. The capacitors are allowed to fully charge. At this point, both capacitors are fitted
with dielectrics, however one circuit has the ideal battery removed at the same time. The other
circuit keeps its battery. After some time has elapsed, which of the following values would be
the same in both capacitors?
(A) Potential energy
(B) Charge
(C) Capacitance
(D) Voltage
(E) Electric field
8. What is the current through the 8-ohm resistor in the circuit shown above?
(A) 0.5 A
(B) 1.0 A
(C) 1.25 A
(D) 1.5 A
(E) 3.0 A
9. The graph above shows the charge vs. time for an RC circuit with voltage V and capacitance C.
The slope of this graph represents
(A) the total charge on the capacitor plates
(B) the potential energy of the capacitor
(C) the resistance of the circuit
(D) the instantaneous voltage of the capacitor
(E) the instantaneous current of the circuit
10. Which of the following combinations of values for total resistance, R, and capacitance, C,
would produce an RC circuit that reached its maximum charge (on the capacitor) most
quickly?
(A) R = 4 O; C = 20 µF
(B) R = 6 O; C = 25 µF
(C) R = 8 O; C = 30 µF
(D) R = 4 O; C = 35 µF
Page 4


Section I: Multiple Choice
1. A wire made of brass and a wire made of silver have the same length, but the diameter of the
brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater
than the resistivity of silver. If R
B
 denotes the resistance of the brass wire and R
S
 denotes the
resistance of the silver wire, which of the following is true?
(A) R
B
 = R
S
(B) R
B
 = R
S
(C) R
B
 = R
S
(D) R
B
 = R
S
(E) R
B
 = R
S
2. For an ohmic conductor, doubling the voltage without changing the resistance will cause the
current to
(A) decrease by a factor of 4
(B) decrease by a factor of 2
(C) remain unchanged
(D) increase by a factor of 2
(E) increase by a factor of 4
3. A given circuit uses 125 watts of power. If the circuit has a total resistance of 5 O, at what
voltage must it be operating?
(A)    5 V
(B)  15 V
(C)  25 V
(D)  45 V
(E) 625 V
4. An ammeter is a device than can be arranged in a circuit to measure the current through
flowing through a particular part of the circuit. Which of the following sets of characteristics
should it possess?
(A) It should have high resistance and should be arranged in series with the part being
measured.
(B) It should have low resistance and should be arranged in series with the part being
measured.
(C) It should have high resistance and should be arranged in parallel with the part being
measured.
(D) It should have low resistance and should be arranged in parallel with the part being
measured.
(E) It should have the same resistance as the part being measured and should be arranged in
series with the part being measured.
5. Determine the equivalent resistance between points a and b in the figure above.
(A) 0.167 O
(B) 0.25 O
(C) 0.333 O
(D) 1.5 O
(E) 2 O
6. Three identical light bulbs are connected to a source of emf, as shown in the diagram above.
What will happen if the middle bulb burns out?
(A) All the bulbs will go out.
(B) The light intensity of the other two bulbs will decrease (but they won’t go out).
(C) The light intensity of the other two bulbs will increase.
(D) The light intensity of the other two bulbs will remain the same.
(E) More current will be drawn from the source of emf.
7. Two identical circuits are created, each with an ideal battery. The circuits each have a
capacitor. The capacitors are allowed to fully charge. At this point, both capacitors are fitted
with dielectrics, however one circuit has the ideal battery removed at the same time. The other
circuit keeps its battery. After some time has elapsed, which of the following values would be
the same in both capacitors?
(A) Potential energy
(B) Charge
(C) Capacitance
(D) Voltage
(E) Electric field
8. What is the current through the 8-ohm resistor in the circuit shown above?
(A) 0.5 A
(B) 1.0 A
(C) 1.25 A
(D) 1.5 A
(E) 3.0 A
9. The graph above shows the charge vs. time for an RC circuit with voltage V and capacitance C.
The slope of this graph represents
(A) the total charge on the capacitor plates
(B) the potential energy of the capacitor
(C) the resistance of the circuit
(D) the instantaneous voltage of the capacitor
(E) the instantaneous current of the circuit
10. Which of the following combinations of values for total resistance, R, and capacitance, C,
would produce an RC circuit that reached its maximum charge (on the capacitor) most
quickly?
(A) R = 4 O; C = 20 µF
(B) R = 6 O; C = 25 µF
(C) R = 8 O; C = 30 µF
(D) R = 4 O; C = 35 µF
(E) R = 8 O; C = 40 µF
Page 5


Section I: Multiple Choice
1. A wire made of brass and a wire made of silver have the same length, but the diameter of the
brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater
than the resistivity of silver. If R
B
 denotes the resistance of the brass wire and R
S
 denotes the
resistance of the silver wire, which of the following is true?
(A) R
B
 = R
S
(B) R
B
 = R
S
(C) R
B
 = R
S
(D) R
B
 = R
S
(E) R
B
 = R
S
2. For an ohmic conductor, doubling the voltage without changing the resistance will cause the
current to
(A) decrease by a factor of 4
(B) decrease by a factor of 2
(C) remain unchanged
(D) increase by a factor of 2
(E) increase by a factor of 4
3. A given circuit uses 125 watts of power. If the circuit has a total resistance of 5 O, at what
voltage must it be operating?
(A)    5 V
(B)  15 V
(C)  25 V
(D)  45 V
(E) 625 V
4. An ammeter is a device than can be arranged in a circuit to measure the current through
flowing through a particular part of the circuit. Which of the following sets of characteristics
should it possess?
(A) It should have high resistance and should be arranged in series with the part being
measured.
(B) It should have low resistance and should be arranged in series with the part being
measured.
(C) It should have high resistance and should be arranged in parallel with the part being
measured.
(D) It should have low resistance and should be arranged in parallel with the part being
measured.
(E) It should have the same resistance as the part being measured and should be arranged in
series with the part being measured.
5. Determine the equivalent resistance between points a and b in the figure above.
(A) 0.167 O
(B) 0.25 O
(C) 0.333 O
(D) 1.5 O
(E) 2 O
6. Three identical light bulbs are connected to a source of emf, as shown in the diagram above.
What will happen if the middle bulb burns out?
(A) All the bulbs will go out.
(B) The light intensity of the other two bulbs will decrease (but they won’t go out).
(C) The light intensity of the other two bulbs will increase.
(D) The light intensity of the other two bulbs will remain the same.
(E) More current will be drawn from the source of emf.
7. Two identical circuits are created, each with an ideal battery. The circuits each have a
capacitor. The capacitors are allowed to fully charge. At this point, both capacitors are fitted
with dielectrics, however one circuit has the ideal battery removed at the same time. The other
circuit keeps its battery. After some time has elapsed, which of the following values would be
the same in both capacitors?
(A) Potential energy
(B) Charge
(C) Capacitance
(D) Voltage
(E) Electric field
8. What is the current through the 8-ohm resistor in the circuit shown above?
(A) 0.5 A
(B) 1.0 A
(C) 1.25 A
(D) 1.5 A
(E) 3.0 A
9. The graph above shows the charge vs. time for an RC circuit with voltage V and capacitance C.
The slope of this graph represents
(A) the total charge on the capacitor plates
(B) the potential energy of the capacitor
(C) the resistance of the circuit
(D) the instantaneous voltage of the capacitor
(E) the instantaneous current of the circuit
10. Which of the following combinations of values for total resistance, R, and capacitance, C,
would produce an RC circuit that reached its maximum charge (on the capacitor) most
quickly?
(A) R = 4 O; C = 20 µF
(B) R = 6 O; C = 25 µF
(C) R = 8 O; C = 30 µF
(D) R = 4 O; C = 35 µF
(E) R = 8 O; C = 40 µF
Section I: Multiple Choice
1. A
Let ?
S
 denote the resistivity of silver and let A
S
 denote the cross-sectional area of the
silver wire. Then
2. D
The equation I = V/ R implies that increasing V by a factor of 2 will cause I to increase by a
factor of 2.
3. C
Use the formula for power that contains resistance and voltage.
P = 
V = 
    =  = 25 V
4. B
As a rule, elements of a circuit arranged in series will have the same current flowing
through them. This eliminates (C) and (D). Furthermore, as a measuring device, the
ammeter should disturb the circuit as little as possible. Introducing an ammeter with high
resistance in series with the element being measured would cause the current to flow in a
different way than it did before the ammeter was introduced. Keeping the ammeter’s
resistance as close to 0 as possible will produce the least change and is therefore the most
desirable outcome.
5. E
The 12 O and 4 O resistors are in parallel and are equivalent to a single 3 O resistor,
because 1/(12 O) + 1/(4 O) = 1/(3 O). This 3 O resistor is in series with the top 3 O
resistor, giving an equivalent resistance in the top branch of 3 + 3 = 6 O. Finally, this 6 O
resistor is in parallel with the bottom 3 O resistor, giving an overall equivalent resistance
of 2 O, because 1/(6 O) + 1/(3 O) = 1/(2 O).
6. D
If each of the identical bulbs has resistance R, then the current through each bulb is e/ R.
This is unchanged if the middle branch is taken out of the parallel circuit.
(What will change is the total amount of current provided by the battery.)
7. C
The immediate effects will be the same in both. When a dielectric is inserted, the electric
field is reduced, which in turn decreases voltage. This decrease in voltage causes a loss of
potential energy. The difference between the two circuits is that the battery that is still
attached can restore that lost voltage to its capacitor by sending additional charge. This
additional charge restores not only the lost voltage, but also the electric field. The