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Two circular coils are made of two ident...

Two circular coils are made of two identical wires of same length and carry same current. If the number of turns of the two coils are 4 and 2, then the ratio of magnetic induction at the centres will be

A

`4//1`

B

`1//4`

C

`1//2`

D

`2//1`

Text Solution

Verified by Experts

The correct Answer is:
A
`L=n_12pia_1=n_2 2pi a_2`
`rArr n_1a_1=n_2a_2rArr (a_1)/(a_2)=(n_2)/(n_1)`
Now , `(B_1)/(B_2)=(mu_0 n_1 I//2a_1)/(mu_0n_2I//2a_2)=(n_1)/(n_2)(a_2)/(a_1)`
`therefore (B_1)/(B_2)=((n_1)/(n_2))^2=(4)/(1)` .
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