MIT8 02SC Quiz18 Sols

8/11/2019 MIT8 02SC Quiz18 Sols

1/15

1

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


2/15

2

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)


3/15

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


4/15

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


5/15

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


6/15P19-6

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


7/157

Concept Question: Field Strength

A

B

C

Where is the pictured field the strongest?

1. A

2. B

3. C

4. I dont know


8/158

Concept Q. Answer: Field Strength

Answer: 3. The field is the strongest at C

Line density is proportional to field strength

A

B

C


9/159


The current carrying coil above will feel a net force

1. upwards

2. downwards

3. of zero

4. I dont know


10/15

10

Concept Q. Answer: Dipole in Field

Answer: 2. Feels downward force

The I ds x B forces shown produce a net

downward force


11/15

11


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


12/15

12

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


13/15

13

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


14/15

14

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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8.02SC Physics II: Electricity and Magnetism

Fall 2010

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MIT8 02SC Quiz18 Sols