NEET Magnetism and Matter — Set 11

Question 1

A material that repels a magnet and is repelled by it in return is likely:

Accepted Answer

Superconductors, exhibiting perfect diamagnetism (Meissner effect), expel magnetic fields completely, causing mutual repulsion with a magnet. This is distinct from weak diamagnetic repulsion and stronger than other material responses.

Question 2

A bar magnet with $ m = 3.0 \, \text{A m}^2 $ is at $ 0.5 \, \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 = 3.0 \, \text{A m}^2 $, $ r = 0.5 \, \text{m} $, $ \frac{\mu_0}{4\pi} = 10^{-7} $. $ B = 10^{-7} \times \frac{2 \times 3.0}{(0.5)^3} = 10^{-7} \times \frac{6.0}{0.125} = 4.8 \times 10^{-6} \, \text{T} $.

Question 3

A material with $ B = 0.45 \, \text{T} $ and $ H = 3000 \, \text{A m}^{-1} $ has $ M $: (Take $ \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} $).

Accepted Answer

$ B = \mu_0 (H + M) $, so $ M = \frac{B}{\mu_0} - H $. Given: $ B = 0.45 \, \text{T} $, $ H = 3000 \, \text{A m}^{-1} $, $ \mu_0 = 4\pi \times 10^{-7} $. $ \frac{B}{\mu_0} = \frac{0.45}{4\pi \times 10^{-7}} \approx 3.581 \times 10^5 \, \text{A m}^{-1} $. $ M = 3.581 \times 10^5 - 3000 \approx 3.551 \times 10^5 \, \text{A m}^{-1} $.

NEET Physics: Magnetism and Matter — Practice Set 11

Q1. A material that repels a magnet and is repelled by it in return is likely:

Q2. A bar magnet with \( m = 3.0 \, \text{A m}^2 \) is at \( 0.5 \, \text{m} \) along its axis. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q3. A material with \( B = 0.45 \, \text{T} \) and \( H = 3000 \, \text{A m}^{-1} \) has \( M \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q4. A magnetic dipole of moment \( 0.25 \, \text{A m}^2 \) is in a uniform field of \( 0.5 \, \text{T} \) at \( 30^\circ \). What is the torque on it?

Q5. Which material has a small positive \( \chi \) and aligns weakly with an external magnetic field?

Q6. A solenoid with 300 turns per meter carries a current of \( 6 \, \text{A} \). What is the magnetic intensity \( H \) inside?

Q7. A bar magnet with \( m = 2.5 \, \text{A m}^2 \) is at \( 0.5 \, \text{m} \) along its axis. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q8. A material that enhances the magnetic field inside it significantly when placed in an external field is likely:

Q9. A dipole with \( m = 0.35 \, \text{A m}^2 \) in \( B = 0.9 \, \text{T} \) at \( 30^\circ \) has torque:

Q10. A solenoid produces \( B = 0.9 \, \text{T} \) with a core of \( \mu_r = 300 \) and \( n = 1500 \, \text{m}^{-1} \). What is the current \( I \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).