Two magnetic poles one of which is three times as strong as the other exert on each other a force equal to 150 mg wt when placedd 5 cm apart in air.The stregth of the stronger pole is

Options

A. 1.7 Am
B. 3.5 AM
C. 6.3 Am
D. 10.5Am

Answer

D

Explanation

`M_(1)=3M_(2).F=150 mgwt,r=5cm,m_(1)=?`
`F=(mu_(0))/(4pi) (m_(1)m_(2))/(r^2)`
`150xx10^(-3)xx10^(-3)=(10^(-7))xxm_(1)xx(m_(1))/(3xx25xx10^(-4))`
`therefore m_(1)=10.5 Am`