Download Chapter 21: Electromagnetism

Chapters 20&21
1.
Sample Quiz
A penguin is incubating his egg at a magnetic pole. This must be the ____________
magnetic pole of the earth.
a) North
2.
b) South
c) East
d) West
e) none
Which of the statements below is false?
a) A constant electric current produces a magnetic field
b) A changing electric current produces a magnetic field.
c) A changing magnetic field induces an electric current.
d) A constant magnetic field induces an electric current.
e) none
3.
B
v
A proton (charge 1.6 x 10–19 C) moves at 2 x 105 m/s eastward
through a region of space in which a magnetic field of 5 x 10–5 T points northward. The
magnetic force (in N) on the proton is ______.
a) 1.6 x 10–18 in
4.
B
c) 1.6 x 10–19 west
d) 1.6 x 10–17 out
e) none
An electron (charge -1.6 x 10–19 C) moves at 2 x 105 m/s southward through a
region of space in which a magnetic field of 5 x 10–5 T points northward. The
magnetic force (in N) on the electron is ___________
v
a) 0
5.
b) 1.6 x 10–18 out
b) 1.6 x 10–18 out
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
d) 1.6 x 10–19 East
e) none
A positively charged particle moves
westward with velocity v as shown. The
direction of the magnetic force on the
particle is _________.
v
a) North
c) 1.6 x 10–17 in
Bout
b) South
c) in
d) out
e) none
Chapters 20&21
6.
I
A conventional (positive) current I flows to the northeast as
shown in a wire which lies in a region of space where a
magnetic field points east. The direction of the magnetic
force on the wire is _______.
B
a) in
7.
b) out
c) Southwest
d) Northwest
e) none
F
A negatively charged particle moves with velocity v out of the plane of the
paper and feels a magnetic force directed to the North. The magnetic field
must point __________.
vout
a) North
8.
2
Sample quiz
x
x
b) South
x
x
•
•
..
a) West
9.
•
d) West
e) none
Bin
wire
•
c) East
Find the direction of the conventional electric
current in the wire that would produce the given
magnetic field.
Bout
b) East
c) in
d) out
e) none
A circular loop of wire lies in the plane of the paper. A
conventional (positive) electrical current I travels clockwise
around the loop. The magnetic field inside the loop
produced by this current points ____________.
a) clockwise
b) counter clockwise
c) in
d) out
e) none
Chapters 20&21
3
Sample quiz
Diagram for problems 10 - 12
I1 = 1A
I2 = 2A
Y•
•
20cm
10.
5cm
5cm
Find the total magnetic field (in tesla) at point X due to the currents in the two wires.
a) 1.2 x 10–5 in
11.
X
b) 1.2 x 10–5 out
c) 4 x 10–6 out
d) 4 x 10–6 in
e) none
Find the total magnetic field (in tesla) at point Y due to the currents in the two wires.
a) 2.33 x 10–6 out
b) 0.33 x 10–6 out
c) 2.33 x 10–6 in
d) 0.33 x 10–6 in e) none
12. Find the force (in N) wire 1 exerts on wire 2. Both wires are 50cm long.
a) 6.37 x 10–7 attract
d) 2.00 x 10–6 repel
b) 6.37 x 10–7 repel
e) none
c) 2.00 x 10–6 attract
===================================================================
Diagram for problems (13 - 15)
L
ℇ
13.
R
Find the time constant (in milliseconds) of this circuit.
a) 450,000
14.
b) 0.150
c) 4.50
d) 0.222
e) none
Find the electric current (in milliamps) flowing in the circuit after 2 time constants have
elapsed.
a) 2.05
15.
A circuit consists of a 1.5 volt battery, 450 mH
inductor, and 100 Ω resistor in series. The switch is
closed at time t = 0.
b) 5.55
c) 9.45
d) 12.97
e) none
If the switch is opened after being closed for 2 time constants does the current return at
once to zero?
a) yes
b) no