What should be the current in a circular coil of radius 5 cm to annule `B_(H)=5xx10^(-5) T?`

Options

A. `0.4A`
B. `4A`
C. `40 A`
D. `1A`

Answer

B

Explanation

The magnetic field at the centrd of a current carrying coil is `B= (mu_(0)I)/(2R) and B_(H) =5 xx10^(-5) T`
`therefore B_(H) =(mu_(0)I)/(2R)`
`therefore I = (2RB _(H))/(mu_(0))=(2xx5xx10^(-2) xx3xx10^(-5))/(4pi xx10^(-7))`
`therefore I =(50)/(4pi) =(50)/(4xx 3.14) =(50)/(12.56) div 4A`