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A proton is moving with
velocity 1.0x107 m/s
through a uniform
magnetic field B = 0.5 T in
the +x-direction.
What is the strength and
direction of the force on
the proton?
Week 9
1
A proton is moving with
velocity 1.0x107 m/s
through a uniform
magnetic field B = 0.5 T in
the +x-direction.
What is the strength and
direction of the force on
the proton?
Week 9
2
A positive ion is shot between the plates of a
parallel plate capacitor.
• In which direction is the electric force on the
particle?
• Could a magnetic field be used to counter this
force? If so, in which direction would the
magnetic field need to be directed?
Week 9
3
Week 9
4
In a high-energy physics experiment, a neutral
particle enters a bubble chamber in which a
magnetic field points into the page. The neutral
particle undergoes a collision, creating two
charged particles. The subsequent trajectories
are shown.
• What are the signs of particles 1 and 2?
• Which charged particle leaves the collision
with more momentum?
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5
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6
Week 9
7
Week 9
8
Draw vectors on Wire 1 showing the direction of
the force felt by Wire 1 from Wire 2.
Draw vectors on Wire 1 showing the direction of
the force felt by Wire 1 from Wire 2.
Will the two wires be attracted or repulsed?
Week 9
9
Will the two wires shown below be attracted or
repulsed?
Week 9
10
Below are three current loops situated on the yaxis.
Will loops 1 and 2 be attracted or repulsed?
Will loops 2 and 3 be attracted or repulsed?
I
I
Loop 1
Week 9
Loop 2
I
Loop 3
11
Week 9
12
A square loop of current is placed in a magnetic
field.
Does the loop undergo displacement? If so, is it
up, down, left or right?
Does the loop undergo rotation? If so, which way
does it rotate?
B
I
II
I
I
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13
Week 9
14
The dots and x’s in the figures below show the
directions of magnetic fields. In each of the cases
below, which way will current flow in the loop?
Week 9
15
A loop of copper wire is being pulled from between two
magnetic poles.
•Which direction will the current induced in the loop flow?
•Does either side of the loop experience a magnetic force?
•Which way will the magnetic field pull on the loop?
S
Fpull
Fpull
S
N
side view
Week 9
top view
16
•Which side of the loop will be a magnetic north pole?
•Are the magnetic poles of the loop attracted to or repelled
by the permanent magnet?
S
Fpull
Fpull
S
N
side view
Week 9
top view
17
Week 9
18
Below are 5 loops in different magnetic fields. Rank
them in order by magnetic flux.
2
1
2
B=1
2
1 B=2
Loop 1
1
Loop 2
1
B=1
Loop 3
1
B=0
2
Week 9
2
B=2
B=2
Loop 4
Loop 5
19
Below are 5 loops in the same magnetic field. Rank
them in order by magnetic flux.
B
Loop 2
r=1
45o
45o
Loop 4
r=2
Loop 1
r=1
Week 9
Loop 3
r=2
20
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21
In each case, which direction does the current
induced in the wire flow?
Week 9
Steady B
Increasing B
Decreasing B
dB
0
dt
dB

dt
dB

dt
22
A magnet passes in front of a loop of wire, with the
north side of the magnet facing the loop. Graph
how the current’s magnitude and direction change
with time. Take CCW flowing current to be positive.
v
magnet
I
Week 9
time
23
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25