A vertical circular coil of radius 0.1 m and having 10 tums carries a steady current. When the plane of the coil is normal to the magnetic meridian, a neutral point is observed at the centre of the coil. If `B_(H)=0.314 xx10^(-4)T`, the current in the coil is

Options

A. 0.5A
B. 0.25A
C. 2A
D. 1A

Answer

A

Explanation

Neutral point : It is that point, where the magnetic field due to a bar magnet is completely cancelled by the horizontal component of earth.s magnetic field.
Magnetic field at a centre of circular coil `(mu_(0))/(4pi)(2pinl)/(a)=B_(H)`
`rArr`    `10^(-7)xx(2xx3.14xx10xxl)/(0.1)=0.34xx10^(-4)`
`rArr`    `I=(0.314xx10^(-4)xx0.1)/(2xx3.14xx10xx10^(-7))` 
=`(1)/(2)xx0.1xx0.1xx10^(-4)xx10^(6)=0.5A` .