Current and Resistance Practice
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____1.How is current affected if the time interval over which the charge passes through a given area decreases while the amount of charge remains the same?
a. / The current increases.b. / The current decreases.
c. / The current initially increases and then is gradually restored.
d. / The current is not affected.
____2.The current in an electron beam in a cathode-ray tube is 7.0 10 A. How much charge hits the screen in 5.0 s?
a. / 2.8 10 C / c. / 3.5 10 Cb. / 5.6 10 C / d. / 5.3 10 C
____3.The amount of charge that moves through the filament of a lightbulb in 2.00 s is 2.67 C. What is the current in the lightbulb?
a. / 5.34 A / c. / 0.835 Ab. / 1.33 A / d. / 0.417 A
____4.When electrons move through a metal conductor,
a. / they move in a straight line through the conductor.b. / they move in zigzag patterns because of repeated collisions with the vibrating metal atoms.
c. / the temperature of the conductor decreases.
d. / they move at the speed of light in a vacuum.
____5.A lightbulb has a resistance of 240 when operating at 120 V. What is the current in the lightbulb?
a. / 2.0 A / c. / 0.50 Ab. / 1.0 A / d. / 0.20 A
____6.Which of the following wires would have the greatest resistance?
a. / an aluminum wire 10 cm in length and 3 cm in diameterb. / an aluminum wire 5 cm in length and 3 cm in diameter
c. / an aluminum wire 10 cm in length and 5 cm in diameter
d. / an aluminum wire 5 cm in length and 5 cm in diameter
____7.Which of the following is the best description of a schematic diagram?
a. / uses pictures to represent the parts of a circuitb. / determines the location of the parts of a circuit
c. / shows the parts of a circuit and how the parts connect to each other
d. / shows some of the parts that make up a circuit
____8.Three resistors connected in series have potential differences across them labeled V, V, and V. Which of the following expresses the potential difference taken over the three resistors together?
a. / Vt= V1 + V2+ V3 / c. / Vt= V1= V2 = V3b. / Vt = / d. / Vt=
____9.Three resistors connected in parallel carry currents labeled I, I, and I. Which of the following expresses the total current I in the combined system?
a. / It= I1 + I2 + I3 / c. / It= I1 = I2 = I3b. / It = / d. / It=
____10.Three resistors with values of 3.0 , 6.0 , and 12 are connected in parallel. What is the equivalent resistance of this combination?
a. / 0.26 / c. / 9.0 b. / 1.7 / d. / 21
____11.The symbol used to represent resistance in a schematic diagram is
a. / two straight lines.b. / a single line that is broken and has a bend in it.
c. / one straight line.
d. / a zigzag line.
e. / none of the above
____12.When resistors are put in series next to each other, their overall resistance is
a. / the same as the resistance of one of the resistors.b. / larger than the resistance of any individual resistor.
c. / smaller than the resistance of any of the resistors.
____13.As more lamps are put into a parallel circuit, the overall current in the main (through the battery) circuit
a. / increases.b. / stays the same.
c. / decreases.
____14.Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have
a. / less resistance.b. / more resistance.
c. / the same resistance.
____15.When one light bulb in a parallel circuit containing several light bulbs burns out, the other light bulbs
a. / do not burn at all.b. / burn brighter.
c. / burn the same as before.
____16.In a simple parallel circuit
a. / voltage across each branch is the same.b. / current through each resistor is inversely proportional to the resistance.
c. / current is divided at each branch.
d. / all of the above
e. / none of the above
____17.Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage is greater across the lamp with the
a. / thin filament.b. / thick filament.
c. / Both voltages are the same.
____18.Two lamps, one with a thick filament and one with a thin filament, are connected in series to a battery. The voltage is greater across the lamp with the
a. / thin filament.b. / thick filament.
c. / Voltage is the same for both.
____19.In order for there to be a flow of charge from one place to another, there must be a
a. / conductor, such as a wire, connecting the two places.b. / potential difference between the two places.
c. / Both A and B above
____20.An example of a voltage source is
a. / a dry cell.b. / a generator.
c. / a car battery.
d. / rubbing a rubber rod with fur.
e. / all of the above
____21.Electrical resistance in a wire depends on the wire's
a. / thickness.b. / conductivity.
c. / length.
d. / all of the above
e. / none of the above
____22.What is the equivalent resistance for the resistors in the figure shown above?
a. / 25 / c. / 7.5 b. / 10.0 / d. / 5.0
Short Answer
23.What is electrical potential energy?
24.What is the source of the energy produced by a battery?
25.With regard to electric current, what is resistance?
26.Draw a schematic diagram that contains three resistors and one battery.
27.Current is not carried in the circuit shown in the schematic diagram above. Explain why this is so.
28.In the circuit shown above, what will happen when the switch is closed? Explain.
Problem
29.A bolt of lightning discharges 9.6 C in 5.5 10 s. What is the average current during the discharge?
30.How much time is required for 41.34 C of charge to move through an electric juicer if the current through the juicer is 1.48 A?
31.How much current is in a resistor of 227 if the potential difference across the resistor is 145 V?
32.A potential difference of 3.6 V is placed across a resistor, producing a current of 14.3 A. What is the resistance of the resistor?
33.A 1.4 k resistor has 0.012 A of current in it. What is the potential difference across the resistor?
34.A 4.7 10 resistor carries 1.52 10 A of current. What potential difference is across the resistor?
35.Three resistors with values of 17 , 23 , 9 , respectively, are connected in series. What is their equivalent resistance?
36.A current of 0.12 A passes through a 5.1 resistor. The resistor is connected in series with a 9.1 V battery and an unknown resistor. What is the resistance value of the unknown resistor?
37.Three resistors with values of 11 , 15 , 22 , respectively, are connected in parallel. What is their equivalent resistance?
38.A 60-V potential difference is applied across a parallel combination of a 10-ohm and a 20-ohm resistor. What is the current in the 10-ohm resistor?
39.What is the equivalent resistance for the resistors in the figure shown above?
40.How much current is in one of the 10 resistors in the diagram shown above?
Current and Resistance Practice
Answer Section
MULTIPLE CHOICE
1.ANS:APTS:1DIF:IIOBJ:17-3.1
2.ANS:C
Given
I = 7.0 10 A
t = 5.0 s
Solution
PTS:1DIF:IIIAOBJ:17-3.1
3.ANS:B
Given
Q = 2.67 C
t = 2.00 s
Solution
PTS:1DIF:IIIAOBJ:17-3.1
4.ANS:BPTS:1DIF:IOBJ:17-3.2
5.ANS:C
Given
V = 120 V
R = 240
Solution
PTS:1DIF:IIIAOBJ:17-3.3
6.ANS:APTS:1DIF:IOBJ:17-3.4
7.ANS:CPTS:1DIF:IOBJ:18-1.1
8.ANS:APTS:1DIF:IIOBJ:18-2.1
9.ANS:APTS:1DIF:IIOBJ:18-2.2
10.ANS:B
Given
R1= 3.0
R2 = 6.0
R3 = 12
Solution
PTS:1DIF:IIIAOBJ:18-2.2
11.ANS:DPTS:1DIF:L1OBJ:35.5 Schematic Diagrams
KEY:resistance | symbolBLM:knowledge
12.ANS:BPTS:1DIF:L2OBJ:35.3 Series Circuits
KEY:resistor | seriesBLM:comprehension
13.ANS:APTS:1DIF:L2OBJ:35.4 Parallel Circuits
KEY:parallel | circuit | lampBLM:comprehension
14.ANS:APTS:1DIF:L2OBJ:35.3 Series Circuits
KEY:resistance | seriesBLM:comprehension
15.ANS:CPTS:1DIF:L2OBJ:35.4 Parallel Circuits
KEY:parallel | bulb | circuitBLM:application
16.ANS:DPTS:1DIF:L2OBJ:35.4 Parallel Circuits
KEY:parallel | circuitBLM:comprehension
17.ANS:CPTS:1DIF:L2OBJ:35.4 Parallel Circuits
KEY:voltage | wire | parallelBLM:analysis
18.ANS:APTS:1DIF:L2OBJ:35.3 Series Circuits
KEY:thick | series | voltageBLM:analysis
19.ANS:CPTS:1DIF:L2OBJ:34.1 Flow of Charge
KEY:flow | chargeBLM:comprehension
20.ANS:EPTS:1DIF:L2OBJ:34.3 Voltage Sources
KEY:voltageBLM:comprehension
21.ANS:DPTS:1DIF:L2OBJ:34.4 Electric Resistance
KEY:resistance | lengthBLM:comprehension
22.ANS:B
Given
R1 = 8.0
R2 = 2.0
R3 = 10.0
R4 = 5.0
Solution
R1,2 = R1 + R2 = 8.0 + 2.0 = 10.0
Req = R1,2,3 + R4 = 5.00 + 5.0 = 10.0
PTS:1DIF:IIIAOBJ:18-3.1
SHORT ANSWER
23.ANS:
potential energy associated with a charge due to the position of the charge in an electric field. It also can be described as the amount of work done by an external agent to place a charge at a given location in an electric field
PTS:1DIF:IOBJ:17-1.1
24.ANS:
Chemical reactions are the source of the energy in a battery.
PTS:1DIF:IOBJ:17-1.3
25.ANS:
Resistance is the opposition to electric current by a material or device.
PTS:1DIF:IOBJ:17-3.3
26.ANS:
Schematics should show symbols for the named circuit elements. The arrangement of the elements in either series or parallel is not important.
PTS:1DIF:IOBJ:18-1.1
27.ANS:
There is no continuous path for current because the switch is open.
PTS:1DIF:IIOBJ:18-1.2
28.ANS:
The lamp will go out, or the lamp will get dimmer. The resistance through the switch is lower than the filament of the lamp.
PTS:1DIF:IIOBJ:18-1.2
PROBLEM
29.ANS:
1.7 10 A
Given
Q 9.6 C
t 5.5 10 s
Solution
PTS:1DIF:IIIAOBJ:17-3.1
30.ANS:
27.9 s
Given
1.48 A
Q 41.34 C
Solution
PTS:1DIF:IIIBOBJ:17-3.1
31.ANS:
0.639 A
Given
R 227
V 145 V
Solution
PTS:1DIF:IIIAOBJ:17-3.3
32.ANS:
0.25
Given
V 3.6 V
I 14.3 A
Solution
PTS:1DIF:IIIAOBJ:17-3.3
33.ANS:
17 V
Given
R 1.4 k 1.4 10
I 0.012 A
Solution
PTS:1DIF:IIIAOBJ:17-3.3
34.ANS:
7.1 10 V
Given
R 4.7 10
I 1.52 10 A
Solution
PTS:1DIF:IIIAOBJ:17-3.3
35.ANS:
49
Given
R1 17
R2 23
R3 9
Solution
For resistors in series,
ReqR1 + R2 + R3 17 + 23 + 9 49
PTS:1DIF:IOBJ:18-2.1
36.ANS:
71
Given
I1 0.12 A
R1 5.1
Vbatt 9.1 V
Solution
For a series circuit,
I1I2I 0.12 A
V1R1I (5.1 )(0.12 A) 0.61 V
V2Vbatt – V1 9.1 V – 0.61 V 8.5 V
PTS:1DIF:IIIBOBJ:18-2.1
37.ANS:
4.93
Given
R1 11
R2 15
R3 22
Solution
For resistors in parallel,
PTS:1DIF:IIIAOBJ:18-2.2
38.ANS:
6 A
PTS:1DIF:L2OBJ:35.4 Parallel Circuits
KEY:current | parallel | potentialBLM:application
39.ANS:
5.2
Given
R1 2.0
R2 6.0
R3 10.0
R4 4.0
Solution
R2,3R2 + R3 6.0 + 10.0 16.0
PTS:1DIF:IIIBOBJ:18-3.1
40.ANS:
0.80 A
Given
R1 2.0
R2 20.0
R3 10.0
R4 10.0
Vbatt 12 V
I3I4
Solution
RR + R 2.0 + 4.00 6.0
VV (RI) (4.00 )(2.0 A) 8.0 V
PTS:1DIF:IIIBOBJ:18-3.2