A circular coil carrying a certain current produces a magnetic field B₀ at its centre. The coil is now rewound so as to have 3 turns and the same current is passed through it. The new magnetic field at the centre is

Step-by-step solution

The magnetic field produced at the centre of the circular coil carrying current is given by B V= ₀ N I 2 r For one turn aligned &N=1 &B₀= ₀ I 2 r aligned As the coil is rewound aligned r^ &= r 3 , N^ =3 B^ &= ₀ I 3 2 ( r 3 ) = 9 ₀ I 2 r =9 B₀ aligned