The magnetic field due to a current carrying circular loop of radius 3 cm at a point on the axis at a distance of 4 cm from the centre is `54muT`. What will be its value at the centre of the loop ?

Options

A. `250mu T`
B. `150mu T`
C. `125mu T`
D. `75muT`

Answer

A

Explanation

The magnetic field of the loop will be, `B= (mu_(0)ia^(2))/(2(a^(2) + r^(2))^(3//2))` …(i) (on the axis) and that at the centre of the loop will be, `B_("centre") = (mu_(0)i)/(2a)`…(ii)
On dividing equation (ii) by (i) and putting the given values `a=3cm, r=4cm`, we get `B_("centre") = 250 xx 10^(6)T= 250 muT`