12th Class Physics Magnetism Question Bank MCQs - Moving Charges and Magnetism

A length L of wire carries a steady current I. It is bent first to form a circular plane coil of one turn. A current I flowing through it produces a magnetic, field B at the centre of the coil. The same length is now bent more sharply to form a double loop of smaller radius. The magnetic field at the centre caused by the same current is

A) B

B) 2B

C) 4B

D) B/2

Correct Answer: C

Solution :

Option [c] is correct.

Explanation:\[{{\operatorname{B}}_{2}}={{n}^{2}}{{B}_{1}}\]

Here n = 2, \[{{B}_{1}}\] = B.

\[{{\operatorname{B}}_{2}}\]=4B