32.1
Which arrangement of two coils has the
larger mutual inductance?
Pink A
B
Yellow
C) They are equal
32.2
A large-diameter two-turn coil (coil 2) is wrapped
around a long smaller-diameter solenoid (coil 1) as
shown. Which is larger M12 or M21 ?

M 12  1
I2
coil 2
coil 1
M 21 
2
I1
A) M12
B) M21
C) M12 = M21
32.2b
Now the number of turns in coil 2 is doubled. What
happens to M = 2/I1?
A: M is half
B: M remains constant.
coil 2
C: M doubles
D: M quadruples
coil 1
E: None of these
Electric toothbrush
CT 33.21
Inductor 1 consists of a single loop of wire.
Inductor 2 is identical to 1 except it has two loops
on top of each other.
What is the B field at the center of coil 2, B2,
compared to the field in the center of coil 1?
A: B2 = B1
B: B2 = 2 B1
C: B2 = 4 B1
D: B2 = B1/2
I
Coil 1
Coil 2
I
CT 33.22
Inductor 1 consists of a single loop of wire.
Inductor 2 is identical to 1 except it has two
loops on top of each other.
How do the self-inductances of the two loops
compare? (Recall, L = /I = N B A/ I)
A: L2 = 2 L1
B:L2 > 2L1
C:L2 < 2L
I
Coil 1
Coil 2
I
HL IN 1
What is the inductance of a solenoid with
length d, area A, and turns/length n?
A: m0 n2 A
B: m0 n2 A d
C: m0 n2 d
D: m0 n A d
E: m0 n A
uestion
CT 32.4
Two long solenoids, each of inductance L, are
connected together to form a single very long
solenoid of inductance Ltotal. What is Ltotal?
+
A) 2L
B) 4L
C) 8L
D) none of these
L
=
L
Ltotal = ?
CT 33.28
The switch is closed at t=0.
What is the current through the resistor, at
t=0+ ?
R = 20
A) 0 A V = 10V
B) 0.5 A
C) 1 A
D) 10 A
E) other
L = 10H
CT 33.27
The switch is closed at t=0.
What is the initial rate of change of current
di/dt in the inductor, at t=0+ ? (Hint: what
is the V(init) across the inductor?)
R = 20
A) 0 A V = 10V
B) 0.5 A/s
C) 1 A/s
D) 10 A/s
E) other
L = 10H
CT 33.29
The switch is closed at t=0.
What is the current through the resistor
after a very long time?
R = 20
A) 0 A V = 10V
B) 0.5 A
C) 1 A
D) 10 A
E) other
L = 10H
HL IN 2
What are the units of L/R?
A: V
B: A
C:A/s
D: S
E: 1/S
HL IN 2
What is the voltage across an inductor as a
function of time for a “charging” LR circuit?
t
V 
A) E L   e 
R
B)
C)
E L  Ve

t
t


D) E L  VL1  e 





t


E) E L  V 1  e 







E L  VLe

t

CT 33.30
At time t=0, the switch is closed. What is the
current thru the inductor L just after the switch
is closed (t= 0+)?
R1 = 10
V = 10V
A: 0 A B) 0.5 A
L = 10H
C) 1.0 A
R2 = 10
D) other
CT 33.31
At time t=0, the switch is closed. What is the
current thru the inductor L after a long time?
R1 = 10
V = 10V
A: 0 A B) 0.5 A
L = 10H
C) 1.0 A
R2 = 10
D) other
CT 33.32
Now suppose the switch has been closed for
a long time and is then opened. Immediately
after the switch is opened, the current thru R2
is
R1 = 10
V = 10V
A: 0 A
L = 10H
B) Not 0 amps.
R2 = 10
CT 32.7
The same current i flows through solenoid 1 and
solenoid 2. Solenoid 2 is twice as long and has twice
as many turns as solenoid 1, and has twice the
diameter. (Hint) for a solenoid B = mo n i )
What is the ratio of the magnetic energy
contained in solenoid 2 to that in solenoid 1,
that is, what is E 2
E1
A) 2
B) 4
C) 8
D) 16
E) None of these.
I
1
2
I
HL AC 1
What is the average power dissipated by the resistor?
A) zero
B) positive
C) negative
D) Not enough
information
CT 33.34
A light bulb is attached to a wall plug. (120 VAC, 60
Hz) How many times a second is the
instantaneous power output to the bulb equal to
zero?
A: Never, there is always power
B: 30 times/sec
C: 60 times/sec
D: 120 times/sec
E: Other
19
CT 33.35
A 100 W light bulb is attached to a wall plug. (120
VAC, 60 Hz)
What is the peak power output to the bulb?
A) 100 W
B) Sqrt[2]*100 W = 141 W
C) 200 W
D) Other
20
CT 33.15
A transformer is attached to a battery
and a resistor as shown. The voltage
difference across the resistor R is ...
V
N2
N1
R
iron core
A: V
D: 0
B: V N1/N2
E: Other
C: V N2/N1
CT 33.17
A step-down transformer is attached to
an AC voltage source and a resistor.
How does IR compare to the current that
is drawn from the AC source I(in)
Iin
I(input)
A) IR > I(input)
B) IR < I(input)
IIRR
C) IR = I(input)