NEET Magnetism and Matter — Set 21

Question 1

A paramagnetic material with $ \chi = 4 \times 10^{-4} $ in $ H = 2000 \, \text{A m}^{-1} $ has magnetization $ M $:

Accepted Answer

$ M = \chi H $. Given: $ \chi = 4 \times 10^{-4} $, $ H = 2000 \, \text{A m}^{-1} $. $ M = 4 \times 10^{-4} \times 2000 = 0.8 \, \text{A m}^{-1} $.

Question 2

A bar magnet with $ m = 2.8 \, \text{A m}^2 $ is at $ 0.4 \, \text{m} $ along its axis. What is $ B $? (Take $ \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} $).

Accepted Answer

$ B = \frac{\mu_0}{4\pi} \frac{2m}{r^3} $. Given: $ m = 2.8 \, \text{A m}^2 $, $ r = 0.4 \, \text{m} $, $ \frac{\mu_0}{4\pi} = 10^{-7} $. $ B = 10^{-7} \times \frac{2 \times 2.8}{(0.4)^3} = 10^{-7} \times \frac{5.6}{0.064} = 8.75 \times 10^{-6} \, \text{T} $.

Question 3

The magnetic field lines inside a solenoid are nearly parallel because:

Accepted Answer

Inside a solenoid, the magnetic field lines are nearly parallel due to the uniform distribution of current loops along its length, creating a consistent field direction and magnitude, especially in a long solenoid where end effects are minimal.

NEET Physics: Magnetism and Matter — Practice Set 21

Q1. A paramagnetic material with \( \chi = 4 \times 10^{-4} \) in \( H = 2000 \, \text{A m}^{-1} \) has magnetization \( M \):

Q2. A bar magnet with \( m = 2.8 \, \text{A m}^2 \) is at \( 0.4 \, \text{m} \) along its axis. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q3. The magnetic field lines inside a solenoid are nearly parallel because:

Q4. A magnetic dipole of moment \( 0.2 \, \text{A m}^2 \) is in a uniform field of \( 0.9 \, \text{T} \) at \( 30^\circ \). What is the torque on it?

Q5. A dipole with \( m = 0.5 \, \text{A m}^2 \) in a field \( B = 0.6 \, \text{T} \) at \( 180^\circ \) has potential energy:

Q6. Which material has \( \chi = -1 \) and completely expels magnetic field lines?

Q7. The primary reason a diamagnetic material develops a weak opposing magnetic moment in an external field is:

Q8. A dipole with \( m = 0.7 \, \text{A m}^2 \) in \( B = 0.6 \, \text{T} \) at \( 30^\circ \) has torque:

Q9. The magnetic potential energy of a dipole with \( m = 0.8 \, \text{A m}^2 \) in a field \( B = 0.25 \, \text{T} \) at \( 180^\circ \) is:

Q10. A solenoid with 1300 turns per meter and current \( 2 \, \text{A} \) has a core with \( \mu_r = 100 \). What is \( B \) inside? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).