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A current passing through a circular coi...

A current passing through a circular coil of two turns produces a magnetic field B as its centr. The coil is then rewound so as to have four turns and the same current is passed through it. The magnetic field at its centre now is

A

`B/2`

B

`2B`

C

`4B`

D

`B/4`

Text Solution

Verified by Experts

The correct Answer is:
B
`therefore l=2 xx 2pir_1=4 xx 2pir_2 therefore r_1=2r_2 or r_2=r_1/2 therefore B=(mmu_0)/(4pi)(2pii)/rtherefore B_2=2B_1 or 2B`
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