Pls answer the following questions giving proper reasons

Asked by abhay.saha4517 | 8th Jan, 2022, 05:41: PM

Expert Answer:

Part(A)
At the point A , current flows in counterclockwise direction in circular coil as shown in figure.
 
While facing the coil , if current flows in counterclcokwise direction in circular coil ,
then facing side of coil acts as north pole of magnet as shown in figure.
 
Hence at point A , we have north pole of electromagnet.
 
At the point B , current flows in clockwise direction in circular coil as shown in figure.
 
While facing the coil , if current flows in clcokwise direction in circular coil ,
then facing side of coil acts as south pole of magnet as shown in figure.
 
Hence at point B , we have south pole of electromagnet.
 
----------------------------------------------------------------------------------
 
Part (B)
 
Magnetic field induction B = μr μo n I
 
where μr is relative permeability of medium inside the coil. For air or vacuum μr = 1 .
 
μo is permeability of free space , n is number of turns per unit length and I is current passing through coil.
 
To increase the magnetic field without changing coil ( n is constant )
 
(i) Current I can be increased
 
(ii) medium inside the coil is changed by placing magnetic material that has μr >> 1
 
-------------------------------------------------------------------------------------------------------------------
 
Part(C)
 
When AC current is passed through coil when iron rod inside , current flows in alternate directions during positive and negative cycle .
 
If iron rod is magnetized during positive cycle , then it is demagnetized during negative cycle .
Net effect is no magnetic field . Hence iron pins will not be attracted.



 

Answered by Thiyagarajan K | 8th Jan, 2022, 08:11: PM