F.5 Physics Generator Question

恩樂

2008-03-21 2:24 am

http://i150.photobucket.com/albums/s87/mllokloks/generater.jpg

The above diagram shows an electricity generator connected to a load.
Which of the following can increase the e.m.f. produced by the generator ?

(1) Roatating the coil at a greater speed
(2) Reducing the resistance of the load
(3) Replacing the coil with one of larger area

A (1)
B (2)
C (1)(2)
D (2)(3)
E (1)(2)(3)

Explain the answer.

更新1:

I think the statement (3) is correct too. But the answer is A. - Faraday's Law states that the e.m.f. induced and hence the current induced in a conductor is directly proportional to the rate at which the conductor cuts through the magnetic field lines. - HKCEE 1997 Paper II Q.37

更新2:

nothing ... there is a mistake u are right : )

回答 (1)

天同

2008-03-21 7:51 am

✔ 最佳答案

Both statements (1) and (3) are correct.

Statement (1) is correct because at higher speed of rotation, the coil cuts more field lines in a second, which produces a larger induced emf.

Statement (3) is correct because a coil of larger area would have more magnetic flux linkage. By Faraday's law, the induced emf is proportional to the rate of change of magnetic flux linkage with the coil. Thus a larger emf is induced.

Statement (2) is wrong because by reducing the resistance of the load doesn't affect the induced emf, only the current will be increased.

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