NEET Magnetism and Matter — Set 15

Question 1

A magnetic dipole of moment $ 0.15 \, \text{A m}^2 $ is in a uniform field of $ 0.8 \, \text{T} $ at $ 60^\circ $. What is the torque on it?

Accepted Answer

Torque is $ \tau = m B \sin\theta $. Given: $ m = 0.15 \, \text{A m}^2 $, $ B = 0.8 \, \text{T} $, $ \theta = 60^\circ $, $ \sin 60^\circ = \frac{\sqrt{3}}{2} \approx 0.866 $. Substitute: $ \tau = 0.15 \times 0.8 \times 0.866 \approx 0.1039 \, \text{N m} \approx 0.104 \, \text{N m} $.

Question 2

A material’s weak repulsion from a magnetic field is due to:

Accepted Answer

Diamagnetic materials exhibit weak repulsion from a magnetic field because an external field induces small currents in their atoms that generate an opposing magnetic moment, per Lenz’s law, resulting in a slight reduction of the field inside the material.

Question 3

A material with $ B = 0.4 \, \text{T} $ and $ H = 2000 \, \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 = 0.4 \, \text{T} $, $ H = 2000 \, \text{A m}^{-1} $, $ \mu_0 = 4\pi \times 10^{-7} $. $ \frac{B}{\mu_0} = \frac{0.4}{4\pi \times 10^{-7}} \approx 3.183 \times 10^5 \, \text{A m}^{-1} $. $ M = 3.183 \times 10^5 - 2000 \approx 3.163 \times 10^5 \, \text{A m}^{-1} $.

NEET Physics: Magnetism and Matter — Practice Set 15

Q1. A magnetic dipole of moment \( 0.15 \, \text{A m}^2 \) is in a uniform field of \( 0.8 \, \text{T} \) at \( 60^\circ \). What is the torque on it?

Q2. A material’s weak repulsion from a magnetic field is due to:

Q3. A material with \( B = 0.4 \, \text{T} \) and \( H = 2000 \, \text{A m}^{-1} \) has \( M \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q4. A bar magnet with original \( m = 2.0 \, \text{A m}^2 \) is cut transversely into two equal parts. What is \( m \) of each part?

Q5. A magnetic dipole placed in a uniform magnetic field experiences no net force but a torque. This is because:

Q6. What is the magnetic field contribution \( B_m \) due to a material with magnetization \( M = 4 \times 10^5 \, \text{A m}^{-1} \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q7. A material with \( B = 0.35 \, \text{T} \) and \( H = 1800 \, \text{A m}^{-1} \) has \( M \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q8. A solenoid with 600 turns per meter carries a current of \( 3.5 \, \text{A} \). What is the magnetic intensity \( H \) inside?

Q9. A material’s weak enhancement of the magnetic field inside it is due to:

Q10. A solenoid with magnetic field \( B = 0.8 \, \text{T} \) inside has a core with \( \mu_r = 400 \) and \( n = 800 \, \text{m}^{-1} \). What is the current \( I \) in the solenoid? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).