Question

Magnetic moment of a thin bar magnet is ‘M’. If it is bent into a semicircular form, its new magnetic moment will be________.
Fill in the blank with the correct answer from the options given below.

• A. M/π
• B. M/2
• C. 2M/π
• D. M

Answer 1

The Correct Option is C

Let's analyze the change in magnetic moment when the bar magnet is bent into a semicircular form.

1. Original Magnetic Moment (M):

The magnetic moment (M) of a bar magnet is given by:

M = m * L

Where:

• m is the pole strength
• L is the length of the bar magnet

2. Semicircular Form:

When the bar magnet is bent into a semicircular form, the length of the arc becomes L, and the radius (r) of the semicircle is:

L = πr

r = L/π

3. New Magnetic Moment (M'):

The new magnetic moment (M') is the product of the pole strength (m) and the distance between the poles, which is the diameter of the semicircle (2r):

M' = m * 2r

M' = m * 2(L/π)

M' = (2mL) / π

4. Relation between M and M':

We know that M = mL:

M' = (2M) / π

Therefore, the new magnetic moment is 2M/π.

The correct answer is:

Option 3: 2M/π