Two like magnetic poles of strenth 10 and 40 SI units are separated by a distance 30 cm. The intensity of magnetic field is zero on the line joining them

Options

A. At a point 10 cm from the stronger pole
B. At a point 20 cm from the stronger pole
C. At the mid-point
D. At infinity

Answer

B

Explanation

`q_(m_(1)) = 10, q_(m)= 40, r= 30cm`
`(mu_(0))/(4pi).(q_(m_(1)))/(x^(2))= (mu_(0))/(4pi).(q_(m))/((30-x)^(2))`
`rArr x= 10cm` So, distance of point is 20cm from stronger pole.