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A magnetised needle of magnetic moment 4...

A magnetised needle of magnetic moment `4*8xx10^-2JT^-1` is placed at `30^@` with the direction of uniform magnetic field of magnitude `3xx10^-2T`. What is the torque acting on the needle?

A

`7.2 xx 10^(-1) N-m`

B

`7.2 xx 10^(-2) N-m`

C

`7.2 xx 10^(-4) N-m`

D

`7.2 xx 10^(-3) N-m`

Text Solution

Verified by Experts

The correct Answer is:
C
Here, `M = 4.8 xx 10^(-2) Am^(2)`
`theta = 30^(@), B = 3 xx 10^(-2) T`
`= MB sin theta`
`= 4.5 xx 10^(-2) xx 3 xx 10^(-2) sin 30^(@)`
`= 7.2 xx 10^(-4) Nm`
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Knowledge Check

  • A bar magnet of magnetic moment 1.5 JT^(-1) lies aligned with the direction of a uniform magnetic field of 1 T. What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment, opposite to the field direction?

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  • A magnet of magnetic moment 2JT^(-1) is aligned in the direction of magnetic field of 0.1T . What is the net work done to bring the magnet normal to the magnrtic field?

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