MIT8 02SC Quiz18 Sols
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Transcript of MIT8 02SC Quiz18 Sols
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8/11/2019 MIT8 02SC Quiz18 Sols
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Concept Question: Dipole in Field
From rest, the coil above will:
1. rotate clockwise, not move
2. rotate counterclockwise, not move
3. move to the right, not rotate
4. move to the left, not rotate
5. move in another direction, without rotating
6. both move and rotate
7. neither rotate nor move
8. I dont know
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Concept Question Answer: Dipole
in Field
Answer: 1. Coil will rotate clockwise (not move)
No net force so no center of mass motion. BUT
Magnetic dipoles rotate to align with externalfield (think compass)
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Concept Question: Dipole in
Helmholtz
A randomly aligned dipole at the center of a
Helmholtz coil will feel:1. a force but not a torque
2. a torque but not a force
3. both a torque and a force4. neither force nor torque
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Concept Question Answer: Dipole
in Helmholtz
The Helmholtz coil makes a UNIFORM FIELD
Dipole feels only torque (need gradient for F)
Answer: 2. a torque but not a force
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P19-5
Concept Question: Moving in
Helmholtz
When moving through the above field profile, a
dipole will:1. Never rotate
2. Rotate once
3. Rotate twice
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Concept Question Answer: Moving
in Helmholtz
The dipole is always aligned with the fieldso it will never rotate
Answer: 1. The dipole will never rotate
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Concept Question: Field Strength
A
B
C
Where is the pictured field the strongest?
1. A
2. B
3. C
4. I dont know
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Concept Q. Answer: Field Strength
Answer: 3. The field is the strongest at C
Line density is proportional to field strength
A
B
C
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Concept Question: Dipole in Field
The current carrying coil above will feel a net force
1. upwards
2. downwards
3. of zero
4. I dont know
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Concept Q. Answer: Dipole in Field
Answer: 2. Feels downward force
The I ds x B forces shown produce a net
downward force
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Concept Question: Dipole in Field
The current carrying coil above will feel a net force1. upwards
2. downwards
3. of zero
4. I dont know
C t Q A Di l i Fi ld
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Concept Q. Answer: Dipole in Field
Answer: 2. The coil feels a force downMany ways to know this:
I ds x B forces
Energy (aligned seeks high B) Equivalent bar magnets
S
N
S
N
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Concept Question: Free Dipoles
If a number of dipoles are randomly
scattered through space, after a while they
1. Attract (move together)2. Repel (move apart)
3. Basically stay put
4. I dont know
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Concept Q. Answer: Free Dipoles
Answer: 1. Free Dipoles Attract
Torque on dipole aligns it with the local field Dipole then moves toward stronger field
closer to another dipole
Link to Shockwave
http://web.mit.edu/viz/EM/visualizations/electrostatics/ForcesTorquesOnDipoles/DipolesShock/DipolesShock.htmhttp://web.mit.edu/viz/EM/visualizations/electrostatics/ForcesTorquesOnDipoles/DipolesShock/DipolesShock.htm -
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MIT OpenCourseWarehttp://ocw.mit.edu
8.02SC Physics II: Electricity and Magnetism
Fall 2010
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