A wire of length l carries a steady current. It is bent first to form a circular plane loop of one turn. The magnetic field at the centre of the loop is B . The same length is now bent more sharply to give a double loop

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Correct answer: C. 4 B

The wire of length l is bent to from a circular loop, so 2 π r=l r= (l)/(2 π) The magnetic field at the centre of the loop is B= (μ_0 I)/(2 r)=(μ_0 I × 2 π)/(2 l) Now the same length of the wire is bent to from a double loop aligned & 2 ×2 ^ =l & r^ =(l)/(4 π) aligned And the magnetic field at the centre aligned & B^ = μ_0 I × 2 2 × r^ =(2 μ_0 I)/(2 × (l)/(4 π))=(2 × 4 π μ I)/(2 l) & B^ B =4 B^ =4 B aligned

A wire of length l carries a steady current. It is bent first to...

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