Question

A magnetic needle has magnetic monent 6.7 x 10-2 Am2 and moment of inertia I = 7.5 x 10-6 kgm2 . It performs 10 complete oscillation in 10s. Find the magnetitude of the magnetic field.

Answer 1

Given:

The magnetic moment m=6.7×10⁻²

The moment of inertia I=7.5×10⁻⁶

The time is 10 sec

To find:

The magnitude of the magnetic field.

Solution:

The time period for the 10 oscillation is

T=6.70/10

T=0.67

Now the relation of the magnetic field with the time period and magnetic moment of inertia.

B=4π²I/mT

Putting the above values

B=4×(3.14)²×7.5×10⁻⁶/6.70×10⁻²×0.67

B=0.01 T

So the magnitude of the magnetic field is 0.01 T