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Magnetic Field Due to Current in a Solenoid

A circular co...

Question

A circular coil of wire is connected to a battery of negligible internal resistance and has magnetic induction $B$ at its centre. If the coil is unwound and rewound to have double the number of turns, and is connected to the same battery, then the magnetic induction at the center is :

A

2 B

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B

4 B

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C

B

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D

0.5 B

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Solution

The correct option is B $2 B$
Magnetic field, $B$ , is directly proportional to number of turns, $n$ . Therefore after rewounding, magnetic field will be double the original value.

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