Physics P
Worksheet
22-1
Worksheet 22-1 Current, Voltage, Resistance, and Power
Current, Voltage, Resistance, and Power
1. At some point in a wire, you observe 4 × 1018 electrons pass by in 0.5 s. What is the current flowing?
2. A hair dryer uses 10 A of current when plugged into a 120-V outlet. What is the resistance of the hair dryer?
3. A light bulb with a resistance of 160 Ω runs off 120 V. What is the current through the bulb?
4. Find the current flowing through a wire if its resistance is 20 Ω and the voltage is 12 V.
5. A radio operates with a potential difference of 9 volts. The radio uses 0.9 watt of power. How much current
does the radio draw?
6. Many houses have fuses or circuit breakers which blow at 10 A of current. Can you run a 1500 W blow dryer
in that house? Explain.
7. A resistor of 20 Ω is connected to a 60 V power source. Find the current flowing through the resistor.
8. A light bulb with a resistance of 240 Ω is connected to a household voltage of 120 V. How much current
flows through the bulb?
9. What is the resistance of a hair dryer if 15 A of current flow through it when plugged into a 120-V outlet?
10. A smoke detector is powered by a 9-V battery. If it draws 300 µA of current, what is its resistance?
11. If a current of 0.083 A of current is measured to flow through a 20-W resistor, what must be the potential
difference across the resistor?
12. A hair dryer draws 15 A of current. How much power does it use? (Hint: use the standard household voltage.)
13. How much current flows through a 60-W light bulb if it is designed to be used in a 120-V system?
14. How much current flows through a 60-W light bulb if it is instead designed to be used in a 12-V system?
15. What is the resistance of the filament of a standard 120-W light bulb?
16. What is the resistance of the filament of a standard 60-W light bulb?
17. In terms of meters, kilograms, seconds and coulombs, what is a joule?
18. In terms of meters, kilograms, seconds and coulombs, what is a watt?
19. In terms of meters, kilograms, seconds and coulombs, what is a volt?
20. In terms of meters, kilograms, seconds and coulombs, what is a ampere?
21. In terms of meters, kilograms, seconds and coulombs, what is a ohm?
22. Show that a N/C is the same thing as a V/m.
23. What is a simplified way of expressing a WŸs (a watt times a second)?
24. What is a simplified way of expressing a AŸs?
25. What is a kWh (kilowatt-hour)?
Physics P
1.
Worksheet 22-1 Current, Voltage, Resistance, and Power
q = ne
(
)(
q = 4 ×10 electrons 1.6 ×10
18
-19
C/electron
)
6.
q = 0.64 C
q
t
0.64 C
I=
0.5 s
I = 1.3 A
Since the conventional current is the flow of
positive charge we will ignore the fact that
electrons are negative and give the current as
a positive value.
I=
2.
3.
4.
5.
V
R
V
R=
I
120 V
R=
10 A
R = 12 Ω
I=
V
I=
R
120 V
I=
160 Ω
I = 0.75 A
V
R
12 V
I=
20 Ω
I = 0.6 A
I=
P = VI
P
I=
V
0.9 W
I=
9V
I = 0.1 A
7.
8.
P = VI
P
I=
V
1500 W
I=
120 V
I = 12.5 A
Since the maximum current is 10 A, the
12.5 A will blow the circuit.
V
R
60 V
I=
20 Ω
I =3A
I=
V
R
120 V
I=
240 Ω
I = 0.5 A
I=
9.
V
R
V
R=
I
120 V
R=
15 A
R=8Ω
10.
V
R
V
R=
I
I=
I=
9V
0.000 3 A
R = 30 000 Ω
= 30 kΩ
R=
11.
P = VI
P
V=
I
20 W
V=
0.083 A
V = 240 V
Physics P
12.
Worksheet 22-1 Current, Voltage, Resistance, and Power
P = VI
(
)(
P = 120 V 15 A
18.
)
P = 1800 W
13.
P = VI
P
I=
V
60 W
I=
120 V
I = 0.5 A
14.
P = VI
P
I=
V
60 W
I=
12 V
I =5A
15.
16.
17.
19.
P = VI
P
I=
V
120 W
I=
120 V
I =1 A
V
R
V
R=
I
120 V
R=
1A
R = 120 Ω
P = VI
P
I=
V
60 W
I=
120 V
I = 0.5 A
V
R
V
R=
I
120 V
R=
0.5 A
R = 240 Ω
I=
20.
21.
J
s
N⋅m
=
s
kg ⋅ m
⋅m
2
= s
s
kg ⋅ m 2
=
s3
W=
J
C
kg ⋅ m 2
s2
=
C
kg ⋅ m 2
=
C ⋅s 2
V=
A=
Ω=
=
I=
=
=
=
J = N⋅m
kg ⋅ m
⋅m
s2
kg ⋅ m 2
=
s2
=
=
22.
C
s
V
A
J
C
C
s
J ⋅s
C2
N ⋅ m ⋅s
C2
kg ⋅ m
⋅ m ⋅s
s2
C2
kg ⋅ m 2
C2 ⋅s
V
J
=
m C⋅m
N⋅m
=
C⋅m
N
=
C
Physics P
23.
24.
Worksheet 22-1 Current, Voltage, Resistance, and Power
J
⋅s
s
=J
W ⋅s =
C
⋅s
s
=C
A ⋅s =
25.
kW ⋅ h = 1000 W ⋅ 3600 s
= 3 600 000 W ⋅s
= 3 600 000 J