A long, straight wire extends into and out of the
screen. The current in the wire is
A. Into the screen.
B. Out of the screen.
C. There is no current
in the wire.
D. Not enough info to
tell the direction.
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B field of two wires
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The magnet field at point P is
A.
B.
C.
D.
E.
Into the screen.
Out of the screen.
To the left.
To the right.
Zero.
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The direction of the magnetic force on the proton is
A.
B.
C.
D.
E.
To the right.
To the left.
Into the screen.
Out of the screen.
The magnetic force
is zero.
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A proton is shot straight at the center of a long, straight
wire carrying current into the screen. The proton will
A.
B.
C.
D.
E.
Go straight into the wire.
Hit the wire in front of the screen.
Hit the wire behind the screen.
Be deflected over the wire.
Be deflected under the wire.
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The direction of the magnetic force on the electron is
A.
B.
C.
D.
E.
Upward.
Downward.
Into the screen.
Out of the screen.
The magnetic force
is zero.
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The horizontal wire can be levitated – held up against
the force of gravity – if the current in the wire is
A. Right to left.
B. Left to right.
C. It can’t be done with
this magnetic field.
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Charge and moving magnet
A bar magnet moves past an electron as shown.
Then the electron at the moment shown
A.
B.
C.
D.
E.
Feels no force
Feels an upwards force
Feels a downward force
Feels a force out of the page
Feels a force into the page.
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B Field of Rings Qualitatively from Biot-Savart
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Where is the north magnetic pole of this current loop?
A.
B.
C.
D.
E.
Top side.
Bottom side.
Right side.
Left side.
Current loops don’t
have north poles.
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What is the current direction in the loop?
A. Out at the top, in at the
bottom.
B. In at the top, out at the
bottom.
C. Either A or B would
cause the current loop
and the bar magnet to
repel each other.
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The current in this solenoid
A. Enters on the left,
leaves on the right.
B. Enters on the right,
leaves on the left.
C. Either A or B would
produce this field.
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The line integral of B around the loop is 0 · 7.0 A.
Current I3 is
A.
B.
C.
D.
E.
0 A.
1 A out of the screen.
1 A into the screen.
5 A out of the screen.
5 A into the screen.
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For the path shown,
A.
B.
C.
D.
0.
0(I1  I2).
0(I2  I1).
0(I1  I2).
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Solenoid 2 has twice the diameter, twice the length, and
twice as many turns as solenoid 1. How does the field B2
at the center of solenoid 2 compare to B1 at the center of
solenoid 1?
A.
B.
C.
D.
E.
B2  B1/4.
B2  B1/2.
B2  B1.
B2  2B1.
B2  4B1.
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Magnetic fields deflect moving charged particles
Electron beam bent into circular or helical path
by magnetic field due to nearby currents.
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At the blackboard:
Coulomb's law plus special relativity explains
strange cross-product rule
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Which magnetic field causes the observed force?
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Which magnetic field (if it’s the correct strength) allows
the electron to pass through the charged electrodes
without being deflected?
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If released from rest, the current loop will
A.
B.
C.
D.
E.
Move upward.
Move downward.
Rotate clockwise.
Rotate counterclockwise.
Do something not listed here.
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