JEE Main Physics Class 12 Magnetism and Matter Questions

The time period of a rectangular magnet oscillating in earth's magnetic field is given by T=2π√

I

MBH

where I= Moment of inertia of the rectangular magnet
M= Magnetic moment
BH= Horizontal component of the earth's magnetic field Initially, the time period of the magnet
T=2π√

I

MBH

where I=

1

12

Ml2
Case 2
Magnet is cut into two identical pieces such that eac piece has half the original length.

Then T′=2π√

I′

M′BH

Moment of inertia of each part
I′=

1

12

(

M

2

)(

l

2

)2=

I

8

and M′=

M

2

∴

T′

T

=√

I′

M

×

M

I

=√

I∕8

M∕2

×

M

I

=√

1

4

=

1

2