Question

A domain in a ferromagnetic substance is in the form of a cube of side '\(L\)'. If it contains '\(N\)' atoms and each atomic dipole moment \(M\) then the magnetisation of the domain is

• A. \(\frac{N}{ML^{3}}\)
• B. \(\frac{MN}{L^{3}}\)
• C. \(\frac{M}{NL^{3}}\)
• D. \(MNL^{3}\)

Hint:

Magnetisation is net magnetic moment per unit volume.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Magnetisation is the net magnetic dipole moment per unit volume.

Step 2: Total Moment
With \(N\) atoms of dipole moment \(M\) each, aligned in a domain, the total moment is \(MN\).

Step 3: Volume
The cube has volume \(L^{3}\).

Step 4: Magnetisation
\(I_m=\dfrac{MN}{L^{3}}\).

Final Answer:
The magnetisation of the domain is MN over L cubed. \[ \boxed{\text{(B) }\dfrac{MN}{L^{3}}} \]