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Question 29 of 36

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SAT Subject Test

The figure shows a bar magnet located above a coil of wire that is connected to an ammeter. The north pole of the magnet is near the top of the coil.

A bar magnet is located next to a coil of wire that is fixed in position and connected to an ammeter A, as shown above. There will be an induced electric current through the ammeter if the magnet is moving in which of the following ways?

I. Toward the coil with constant speed
II. Toward the coil with increasing speed
III. Away from the coil with constant speed
IV. Away from the coil with increasing speed

Select an Answer

text I end text or text II end text only

Correct Answer: 
No

text I end text or text III end text only

Correct Answer: 
No

text II end text or text IV end text only

Correct Answer: 
No

text III end text or text IV end text only

Correct Answer: 
No

text I end text or text II end text or text III end text or text IV end text

Correct Answer: 
Yes

The correct answer is all four motions. Since the magnetic field extending from the end of the bar magnet is non-uniform, any motion of the magnet will cause a change in the magnetic flux passing through the coil. This, in turn, causes an induced emf and thus a current in the coil.

Question Difficulty: 
hard