Lesson 8.01 Current Resistance and Power
Self-Check Quiz
1. A constant 10 A current flows in a circuit with a resistance of 200
ohm. The net charge passing through any point in the circuit during a 1
minute interval is _______.
a. 200C
b. 400C
c. 600C
d. 1200C
Answer: _____
2. If a 75-W light bulb operates at a voltage of 120 V, what is the
current in the bulb?
a. 0.63 A
b. 0.78 A
c. 0.85 A
d. 1.1 A
Answer: _____
3. The heating coil of a water heater has a resistance of 20 ohm and
operates at 210 V. How long does it take to raise the temperature of
200 kg of water from 15oC to 80oC? (cwater = 4186 J/kg*oC)
a. 1.7 hr
b. 3.8 hr
c. 5.1 hr
d. 6.9 hr
Answer: _____
4. Electrical resistance in a wire depends on the wire's _____________.
a. conductivity
b. length
c. thickness
d. All of the above
e. None of the above
Answer: _____
5. Toaster uses a nichrome heating coil and operates at 120 V. When the
toaster is turned on at 20oC, the current in the cold coil is 1.5 A.
When the coil warms up, the current has a value of 1.3 A. If the
thermal coefficient of resistivity for nichrome is 4.5*10-4 1/Co, what is
the temperature of the coil?
a. 486o
b. 362o
c. 256o
d. 163o
e. 68.2o
Answer: _____
6. A 1500
resistor is rated at 2.75 W. What is the maximum potential
difference on the resistor?
a. 8 V
b. 14 V
c. 25 V
d. 38 V
e. 64 V
Answer: _____
7. A 0.20 meter long metal wire has a radius of 1 cm and a resistance
of 3.2*10-5. What is the resistivity of the metal?
a. 1.6*10-8
b. 5.0*10
-8
c. 16.0*10
d. 160*10
-8
-8
m
m
m
m
Answer: _____
8. A 500-W heater carries a current of 4.0 A. What is the resistance of
the heating element?
a. 85.7
b. 42.8
c. 31.3
d. 11.2
Answer: _____
9. A 5.5 meter long Aluminum wire has resistance of 0.40
2.82x10-8
m,
=
= 4.29x10-3C-1. Its conductivity is
a. 2.5x103
b. 3.55x107 (
,
-1
m)
-1
/m
c. 233.
Answer: _____
10. Electrical resistance in a wire depends on the wire's __________.
a. length
b. diameter
c. resisistivity
d. All of the above
e. None of the above
Answer: _____
11. A copper cable carries a current of 300. If the power loss is 2 W
per meter, find the radius of the cable. (The resistivity of copper is
1.7*10-4
m.)
a. 0.8 cm
b. 1.6 cm
c. 3.2 cm
d. 4.0 cm
Answer: _____