1.The magnetic field at a point near the centre but outside a current-carrying solenoid is zero.Why?
2.What is the average value of voltge over a full cycle of alternating current and why?

Asked by Divyaa | 8th Aug, 2016, 08:08: PM

Expert Answer:

An ideal solenoid is a long solenoid with a large number of turns. The term long means that the length of the solenoid is very large as compared to its diameter.
 
Now, the wire of each loop has a small field generated around it.
 
 
From the figure it is clear that the field between two adjacent loops vanishes as they get cancelled because of opposite direction.
 
Also, the field at some exterior point Q is weak and as the length of the solenoid is very large as compared to its width, the field at Q is negligible.
 
This is because all the field lines emanating from inside the solenoid will have large circular radius which will tend to infinity, and hence, the field will not be felt near the solenoid.
 
NOTE: Kindly post the other question as a separate query.

Answered by Romal Bhansali | 10th Aug, 2016, 12:06: PM