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. `250muT`
B. `150 muT`
C. `125 muT`
D. `75 muT`

Answer

A

Explanation

`B_(x)=(mu_(0)NIR^(2))/(2(R^(2)+x^(2))^(3//2))` and `B_(C)=(mu_(0)NI)/(2R)`
`B_(x)=(mu_(0)NI xx3xx3)/(2(5)^(3))=54 muTimpliesmu_(0)NI=(54xx2xx125)/9,B_(C)=(mu_(0)NI)/(2R)=(54xx2xx125)/(9x2xx3)=250 muT`