A point P is situated at a distance of 20cm from the centre of bar magnet of magnetic moment `8Am^(2)` on line which makes an angle of `45^(@)`with its axis.The magnetic induction is

Options

A. `1.0 xx 10^(-4)T,16^(@)`
B. `1.5 xx10^(-4)T,26^(@)`
C. `1.5 xx 10^(4) T,30^(@)`
D. `2.5 xx10^(-4) T,46^(@)`

Answer

B

Explanation

`B=(mu_(0))/(4pi)(M)/(r^(3))sqrt(3cos^(2)theta+1)`
`=(10^(-7)xx8)/(8xx10^(-3))sqrt(3cos^(2)45+1)=1.581xx10^(-4)T`
`phi=tan^(-1)((1)/(2)tantheta)=tan^(-1)((1)/(2)tan45)`
`26^(@)34'`