Name___________________________
Ch 20 Sample Multiple Choice Questions – Simple DC Circuits
Note: Unless otherwise noted, assume all batteries and meters are ideal.
1.
An electric heater that draws 13.5 A of dc current has been left on for 10 min. How many electrons have passed through
the heater during that time? (𝑒 = 1.60 × 10
C)
(A)1.5 × 10
(B) 5.1 × 10
(C) 1.8 × 10 (D) 8.1 × 10
2.
If the length and diameter of a wire of circular cross section are both tripled, the resistance will be
(A) tripled. (B) increased by a factor of 9. (C) 1/3 of what it originally was. (D) 1/9 of what it originally was.
3.
Over ordinary temperature ranges, the resistance of most metals such as copper
(A) is independent of the temperature of the metal.
(B) decreases as the metal gets hotter.
(C) increases as the metal gets hotter.
(D) is a maximum at 20°C.
4.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material?
(A) current
(B) resistivity
(C) 1/(current)
(D) 1/(resistivity)
5.
A 4000-Ω resistor is connected across a 220-V power source. What current will flow through the resistor?
(A) 0.055 A (B) 1.8 A (C) 5.5 A (D) 18 A
6.
If the current flowing through a circuit of constant resistance is doubled, the power dissipated by that circuit will
(A) quadruple in magnitude.
(B) double in magnitude.
(C) decrease to one-half of what it was.
(D) decrease to one-fourth of what it was.
7.
A 100-W light bulb is operated by a 110-V dc source. What is the resistance of this bulb?
(A) 100 Ω (B) 80 Ω
(D) 120 Ω (E) 240 Ω
8.
If the power rating of a 400-Ω resistor is 0.80 W, what is the maximum current it can safely draw?
(A) 45 mA (B) 18 mA (C) 4.4 mA (D) 2.0 mA (E) 320 mA
9.
A 1500-W heater is connected to a 120-V line for 2.0 hours. How much heat energy is produced?
(A) 1.5 kJ (B) 3.0 kJ (C) 0.18 MJ (D) 11 MJ
10. A 100-W driveway light bulb is on 10 hours per day. If the power company charges 10¢ for each kilowatt-hour of
electricity used, estimate the yearly cost to operate the bulb if it is used every day for a 365-day year.
(A) $3.65 (B) $7.30 (C) $37 (D) $73
11. When unequal resistors are connected in series across an ideal battery,
(A) the same power is dissipated in each one.
(B) the potential difference across each is the same.
(C) the current flowing in each is the same.
(D) the equivalent resistance of the circuit is less than that of the smallest resistor.
(E) the equivalent resistance of the circuit is equal to the average of all the resistances.
12. When unequal resistors are connected in parallel in a circuit,
(A) the same current always runs through each resistor.
(B) the potential drop is always the same across each resistor.
(C) the largest resistance has the largest current through it.
(D) the power generated in each resistor is the same.
Use the following for the next three questions:
Two resistors of 2 and 4 are placed in series with a 12-V battery with no internal resistance.
13. Which of the following statements is true?
(A) The 2 will get more current than the 4 resistor since it has less resistance.
(B) The 4 will get more current than the 2 resistor since it has more resistance.
(C) The 2 and 4 resistors will get the same voltage.
(D) The 2 resistor will get more voltage than the 4 resistor.
(E) The 4 resistor will get more voltage than the 2 resistor.
14. The current in the 2
(A) 6 A
(B) 4 A
resistor is
(C) 3 A (D) 2 A
15. The voltage across the 4 resistor is
(A) 2 V
(B) 4 V
(C) 6 V (D) 8 V
(E) 1 A
(E) 12 V
Use the following to answer the next four questions:
A 6-volt battery with no internal resistance is connected to three resistors as shown in the figure below.
16. What is the equivalent resistance of the circuit?
(A) 1.3
(B) 2.8
(C) 4.3
(D) 6
(E) 13
17. How do the currents 𝐼 , 𝐼 , and 𝐼 in the 3 , 4 , and 6
(A) 𝐼 = 𝐼 = 𝐼
(B) 𝐼 > 𝐼 = 𝐼
(C) 𝐼 < 𝐼 = 𝐼
resistors, respectively, compare?
(D) 𝐼 > 𝐼 > 𝐼
(E) 𝐼 > 𝐼 > 𝐼
18. What is the value of the potential difference between points X and Y ?
(A) 1 V
(B) 2 V
(C) 3 V
( D) 4 V
(E) 6V
19. How much energy is dissipated by the 6 resistor in 1 minute?
(A) 0.6 J (B) 6 J
(C) 40 J (D) 160 J (E) 360 J
20. A lamp, a voltmeter V, an ammeter A, and a battery with zero internal resistance
are connected as shown right. Connecting another lamp in parallel with the first
lamp as shown by the dashed lines would
(A) increase the ammeter reading
(B) decrease the ammeter reading
(C) increase the voltmeter reading
(D) decrease the voltmeter reading
(E) produce no change in either meter reading
21. In the circuit shown above, the value of r is
(A) 0
(B) 1
(C) 2
(D) 3
(E) 8
22. The figure above shows three resistors connected in a circuit with a battery. Which of the following correctly ranks the
energy E dissipated in the three resistors during a given time interval?
(A) E300 > E200 > E100
(B) E300 > E100 > E200
(C) E200 > E300 > E100
(D) E200 > E100 > E300
Use the following to answer the next two questions:
Four identical light bulbs are connected to an ideal battery as shown in the diagram below. The switch is open.
23. Which of the following correctly lists the bulbs in order of brightness, from brightest to least bright?
(A) D>A=B=C (B) D>C>A=B (C) C>A=B>D (D) C>D>A=B
24. Which of the following statements correctly describes the change in brightness of the bulbs when the switch is closed?
(A) There is no change in brightness for any of the bulbs.
(B) Bulbs A, B, and D go out; bulb C gets brighter.
(C) Bulb D goes out; bulbs A, B, and C get brighter.
(D) Bulb D goes out, bulb C gets brighter, and bulbs A and B dim, but do not go out.
25. Identical light bulbs can be attached to identical ideal batteries in three different ways (A, B, or C), as shown in the figure.
The ranking (from lowest to highest) of the total power produced by the battery is
(A) B, A, C
(B) A, B, C
(C) C, B, A
(D) A, C, B
(E) C, A, B
26. Identical ideal batteries are connected in different arrangements to the same light bulb, as shown in the figures below. The
ranking (from brightest to least bright) of the brightness of the bulb is
(A) B, A, C
(B) A, B, C
(C) C, B, A
(D) A, C, B
(E) C, A, B
27. You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit
that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which
statement about these bulbs is correct?
(A) Both bulbs glow with the same brightness, but less than their normal brightness.
(B) Both bulbs glow with the same brightness, but more than their normal brightness.
(C) The 100-W bulb glows brighter than the 50-W bulb.
(D) The 50-W bulb glows more brightly than the 100-W bulb.
28. A battery has an emf ε = 43.0 V and an internal resistance r = 8.0 Ω, as shown in the figure. When the terminal voltage Vab is equal to 34.0 V, the current through the battery, including its direction, is closest to
(A) 1.1 A, from b to a.
(B) 4.2 A, from b to a.
(C) 1.1 A, from a to b.
(D) 4.2 A, from a to b.
29. In the circuit shown in the figure, the resistor R is a variable resistor. As R is decreased, what happens to the currents?
(A) I1 remains unchanged and I2 increases.
(C) I1 decreases and I2 increases.
(E) I1 increases and I2 increases.
(B) I1 decreases and I2 decreases.
(D) I1 increases and I2 decreases.
30. A number of resistors are connected across points A and B as shown in the figure. What is the equivalent resistance
between points A and B?
(A) 4 Ω
Answers
1. B
2. C
11. C 12. B
21. E
22. C
(B) 6 Ω
3. C
13. E
23. B
(C) 8 Ω
4. C
14. D
24. C
(D) 10 Ω
5. A
15. D
25. A
6. A
16. D
26. E
(E) 12 Ω
7. D
17. D
27. D
8. A
18. B
28. A
9. D
19. C
29. C
10. C
20. A
30. C