Question

A circular current carrying coil produces a magnetic field B at its centre. The coil is rewound so as to have three turns and the same current is passed through it. The new magnetic field at the centre is


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Answer 1

Answer:

Let initial radius is r.

So, 2πr=3×2πr

1

⟹r

1

=

3

r

Initially B

0

=

2r

H

0

I

Finally B=

2r

1

H

0

(3I)

=9

2r

H

0

I

=9B

0

correct option B