Download Chapter 18

Last updated: September 30, 2008
PHY 2054 Discussion – Fall ‘08
Practice Exam Problems (Chapter 18)
1.
When a 24.0-Ω resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the
resulting terminal voltage of the battery? (Emf)
2.
If R1<R2<R3, and if these resistors are connected in series in a circuit, which one dissipates the
greatest power? (Resistors in Series)
3.
a. R1
b. R2
c. R3
d. All are equal in power dissipation
Which two resistors are in parallel with each other? (Resistors in Parallel)
a. R and R4
b. R2 and
c. R2 and R4 d. R and R1
R3
4.
a. 0.4 V b. 5.8 V c. 11.6 V d. 12.0 V
Resistors of values 6.0 Ω, 4.0 Ω, 10.0 Ω and 7.0 Ω are combined as shown. What is the equivalent
resistance for this combination? (Equivalent resistance)
4
a. 2.3 Ω
b 3.0 Ω
c. 10.7 Ω d. 27 Ω
10 
6
7
5.
If ε = 20 V, at what rate is thermal energy being generated in the 20-Ω resistor? (Combinations of
resistors)
a. 6.5 W b. 1.6 W c. 15 W d. 26 W
40 

30 
30 
30 
20 
6.
What is the current through the 2-Ω resistor?
d. 2.0 A
(Complex DC circut) a. 1.0 A b. 0.50 A c. 1.5 A
8.0 V
2.0 
9.0 V
6.0 
b
a
4.0 
7.
In a circuit, a current of 2.0 A is drawn from a battery. The current then divides and passes through
two resistors in parallel. One of the resistors has a value of 64 Ω and the current through it is 0.40 A.
What is the value of the other resistor? (Kirchhoff’s Rule)
8.
a. 8.0 Ω
b. 16 Ω
c. 24 Ω d. 32 Ω
A 10-V-emf battery is connected in series with a 2-μF capacitor, a 2-Ω resistor, an ammeter and a
switch. A voltmeter is connected in parallel across the capacitor. At the instant the switch is closed,
what are the current and capacitor voltage readings, respectively? (RC Circuit)
a. zero A, 10 V b.
zero A, zero V c. 5 A, zero V d. 5A, 10V
10 V
A
9.
C
2µF
V
2.0 
A series of RC circuit, which is made from a battery, a switch, a resistor, and a 3.0-μF capacitor, has a
time constant of 9.0 ms. If an additional 6.0-μF is added in series to the 3.0-μF capacitor, what is the
resulting time constant? (Time Constant)
a. 4.0 ms
b. 6.0 ms
c. 10 ms
d. This cannot be found
without the value of the resistance being given.
10. A hair dryer draws 1 200 W, a curling iron draws 800 W, and an electric light fixture draws 500 W. If
all three of these appliances are operating in parallel on a 120-V circuit, what is the total current
drawn? (Household Circuits)
a. 19.4 A b. 20.8 A c. 25.4 A d. 36.7 A
11. Household 120-V outlets are made to accept three-pronged plugs. One of the prongs attaches to the
“live” wire at 120 V, and another attaches to the “neutral” wire that is connected to ground. What is
the round third prong for? (Electrical Safety)
appliance run if the neutral wire breaks.
for safety purposes.
a. It serves as a backup to the hot wire.
b. It lets the
c. It connects the case of the appliance directly to ground
d. Nothing electrical, it is for mechanical sturdiness.
Answers: 1-c
2-c
3-b
4-c
5-b
6-a
7-b
8-c
9-b
10-b
11-c