8. The coils of a solenoid are stretched so that the length of the solenoid is twice its original length. Assuming the same current is passed though the solenoid before and after it is stretched, how does the magnetic field inside the solenoid change, if at all, as a result of the stretching? a) The magnetic field after the stretching is one-fourth the value it was before stretching. b) The magnetic field after the stretching is one-half the value it was before stretching. c) The magnetic field after the stretching is the same as the value it was before stretching. d) The magnetic field after the stretching is twice the value it was before stretching. e) The magnetic field after the stretching is four times the value it was before stretching.

Question

Physics

Rogelio Wise

2 July, 12:23

8. The coils of a solenoid are stretched so that the length of the solenoid is twice its original length. Assuming the same current is passed though the solenoid before and after it is stretched, how does the magnetic field inside the solenoid change, if at all, as a result of the stretching? a) The magnetic field after the stretching is one-fourth the value it was before stretching. b) The magnetic field after the stretching is one-half the value it was before stretching. c) The magnetic field after the stretching is the same as the value it was before stretching. d) The magnetic field after the stretching is twice the value it was before stretching. e) The magnetic field after the stretching is four times the value it was before stretching.

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Answers (1)

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Elise Turner · Answer 1

b) The magnetic field after the stretching is one-half the value it was before stretching

Explanation:

magnetic field in a solenoid = μ n i

where μ is permeability, n is no of turns per unit length and i is current

= μ N i / L where N is total no of turns in the whole length L of solenoid.

Now μ, N, i are constant

B = K / L

So

B is inversely proportional to length of solenoid. If L becomes two times, B will become half.

Option (B) is correct.