Question

The magnetic moment produced in a sample of 2 gram is \(8\times 10^{-7}\,\text{A/m}^2\). If its density is \(4 \text{g/cm}^3\) then the magnetization of the sample is

• A. \(1.6\)
• B. \(1.2\)
• C. \(1.4\)
• D. \(1.8\)

Hint:

Magnetisation is magnetic moment per unit volume; find the volume from mass and density.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Magnetisation is \(M = \dfrac{m_{moment}}{V}\), the magnetic moment per unit volume.

Step 2: Volume:
\[ V = \frac{\text{mass}}{\text{density}} = \frac{2\ \text{g}}{4\ \text{g/cm}^3} = 0.5\ \text{cm}^3 = 0.5\times10^{-6}\ \text{m}^3 \]

Step 3: Magnetisation:
\[ M = \frac{8\times10^{-7}}{0.5\times10^{-6}} = 1.6\ \text{A/m} \]

Step 4: Check:
Option (A). Other options would need a different volume, such as \(0.667\times10^{-6}\) m\(^3\) for 1.2.

Final Answer:
Volume is 0.5 cm^3, so M = 1.6 A/m. \[ \boxed{\text{(A) }1.6\ \text{A/m}} \]