Question

The couple acting on a magnet of length 10cm and pole strength 15A-m, kept in a field of `B=2xx10^(-5)`, at an anlge of `30^(@)` is
A. `1.5xx10^(-5)N-m`
B. `1.5xx10^(-3)N-m`
C. `1.5xx10^(-2)N-m`
D. `1.5xx10^(-6)N-m`

Answer 1

As, `tau=MB sin theta=(mxx2l)xx2xx10^(-5)sin30^(@)`
`=15xx10xx10^(-2)xx(1)/(2)=1.5xx10^(-5)N-m`