At a distance of 10 cm from a long straight wire carrying current, the magnetic field is 0.04 T. At the distance of 40 cm, the magnetic field will be ______ .

Options

A. 0.01 T
B. 0.02 T
C. 0.08 T
D. 0.16 T

Answer

A

Explanation

`y_(1)=10cm,y_(2)=40cm,B_(1)=0.04T`
For long current carrying wire,
`B=(mu_(0)I)/(2pi)rArrBprop1/y` (For constant I)
`thereforeB_(1)/B_(2)=y_(2)/y_(1)rArrB_(2)=B_(1)xxy_(2)/y_(1)`
`thereforeB_(2)=(0.04xx10)/40=0.01T`