Home
Class 12
PHYSICS
The torque acting on a magnet of magneti...

The torque acting on a magnet of magnetic moment 'M' placed in a uniform magnetic field B is

Text Solution

Verified by Experts

Let a magnetic dipole NS be placed in uniform magnetic field `vecB` at an angle `theta` with the field.

Force on N-pole = `mB("along"vecB)`
Force on S-pole = mB (opposite to `vecB`)
Torque acting on the bar magnet.
i.e., `tau=mB(bot"distance "NS)`
or `tau=mB(NA)`
But `NA=2lsintheta`
`therefore" "tau=mB2lsintheta=m2lBsintheta`
or `tau=MBsintheta" "[becauseM=2l]`
or `vectau=vecMxxvecB`
`vectau` is perpendicular to the plane containing `vecMandvecB`.
If `theta=90^(@),B=1`, then
`tau=Mxx1xx1`
or `M=tau`
Therefore magnetic dipole moment is defined as the torque experienced by the dipole placed perpendicular to uniform magnetic field of unit strength.
S.I. unit of `vecM` is `JT^(-1)` (joule per tesla).
Promotional Banner

Topper's Solved these Questions

  • MAGNETISM

    MBD -HARYANA BOARD|Exercise SHORT ANSWER TYPE QUESTIONS|4 Videos

  • MAGNETISM

    MBD -HARYANA BOARD|Exercise LONG ANSWER TYPE QUESTIONS|7 Videos

  • ELECTROSTATICS

    MBD -HARYANA BOARD|Exercise OBJECTIVE TYPE QUESTIONS|23 Videos

  • MODEL TEST PAPER (SOLVED)

    MBD -HARYANA BOARD|Exercise LONG ANSWER TYPE QUESTIONS|6 Videos

Similar Questions

Explore conceptually related problems

The ratio of torque acting on a magnet of magnetic moment M' placed in uniform magnetic field when angle between vecM and vecB" are "90^(@) and 0^(@) respectively is magnetic field, it experiences

The force acting on each pole of a magnet when placed in a uniform magnetic field of 7A//m is 4.2xx10^(-4)N . If the distance between the poles is 10 cm , the moment of the magnet is

The torque acting on a magnetic dipole of moment P_(m) when placed in a magnetic field is

A bar magnet of magnetic moment M is placed in a uniform magnetic field B in such a manner that is angle between M and B. Select the correct option(s)

A current-carrying coil of magnetic moment vecM is placed in a uniform magnetic field of induction vecB such that the angle between vecM and vecB is 30^(@) . If M=5 A.m^(2) and B=0.2 Wb//m^(2) , what is the torque acting on the coil?

If a bar magnet of magnetic moment M is kept in a uniform magnetic field B, its time period of oscillation is T. The another magnet of same length and breath is kept in a same magnetic field. If magnetic moment of new magnet is M//4 , then its oscillation time period is

A short bar magnet having magnetic moment M=0.80 JT^1 is placed in uniform magnetic field of 0.30 T. If bar magnet is free to rotate in plane of field, then (where U is potential energy and tau is torque)