Question

Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What potential difference in volts should be applied across them so that the magnetic field at their centres is the same?

(a) 2

(b) 3

(c) 4

(d) 6

Answer 1

Correct option (c) 4

Explanation:

The magnetic field at the centre of the coil,

As B1 will not be equal to B2 unless E1 is different from E2 E1 and E2 will not be the same. It is wrong to ask what potential difference should be applied across them. It should be perhaps the ratio of potential differences.