The electric current in a circular coil of four turns produces a magnetic induction 32 T at its centre. The coil is unwound and is rewound into a circular coil of single turn, the magnetic induction at the centre of the coil by the same current will be :

Step-by-step solution

Magnetic field at the centre of the coil is given by, B = μ 0 i 2 R . Now in the first case: B = 4 μ 0 i 2 R and for the second case: B ' = μ 0 i 2 R ' . As the length of the wire will remain same, therefore 2 π R ' = 4 2 π R ⇒ R ' = 4 R Hence, required ratio will be B ' B = R 4 R ' = 1 16 ⇒ B ' = 2   T