NEET Magnetism and Matter — Set 19

Question 1

The strongest magnetic field of a bar magnet is observed:

Accepted Answer

The magnetic field of a bar magnet is strongest at its poles, where field lines are most concentrated, as opposed to the central region where the field is weaker and less dense.

Question 2

The magnetization $ M $ of a sample is $ 5 \times 10^4 \, \text{A m}^{-1} $ in a magnetic field $ B = 0.1 \, \text{T} $. What is the magnetic intensity $ H $? (Take $ \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} $).

Accepted Answer

$ B = \mu_0 (H + M) $, so $ H = \frac{B}{\mu_0} - M $. Given: $ B = 0.1 \, \text{T} $, $ M = 5 \times 10^4 \, \text{A m}^{-1} $, $ \mu_0 = 4\pi \times 10^{-7} $. $ \frac{B}{\mu_0} = \frac{0.1}{4\pi \times 10^{-7}} \approx 7.96 \times 10^4 \, \text{A m}^{-1} $. $ H = 7.96 \times 10^4 - 5 \times 10^4 = 2.96 \times 10^4 \, \text{A m}^{-1} \approx 3 \times 10^4 \, \text{A m}^{-1} $.

Question 3

The torque on a magnetic dipole in a uniform magnetic field is zero when:

Accepted Answer

The torque on a magnetic dipole is given by $ \tau = m B \sin\theta $. It becomes zero when $ \sin\theta = 0 $, which occurs when the dipole is aligned with the field ($ \theta = 0^\circ $) or anti-aligned ($ \theta = 180^\circ $), as the cross product $ m \times B $ vanishes.

NEET Physics: Magnetism and Matter — Practice Set 19

Q1. The strongest magnetic field of a bar magnet is observed:

Q2. The magnetization \( M \) of a sample is \( 5 \times 10^4 \, \text{A m}^{-1} \) in a magnetic field \( B = 0.1 \, \text{T} \). What is the magnetic intensity \( H \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q3. The torque on a magnetic dipole in a uniform magnetic field is zero when:

Q4. A material with \( B = 0.48 \, \text{T} \) and \( H = 3200 \, \text{A m}^{-1} \) has \( M \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q5. A bar magnet with magnetic moment \( 1.5 \, \text{A m}^2 \) is placed at a distance of \( 0.3 \, \text{m} \) along its axis. What is the magnetic field \( B \) at that point? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q6. A material has \( B = 0.15 \, \text{T} \) and \( M = 8 \times 10^4 \, \text{A m}^{-1} \). What is \( H \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q7. A bar magnet with \( m = 1.8 \, \text{A m}^2 \) produces a field at \( 0.6 \, \text{m} \) on its equatorial line. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q8. A material with \( \mu_r = 800 \) and \( H = 250 \, \text{A m}^{-1} \) has \( B \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q9. The magnetic field inside a bar magnet is directed from:

Q10. A solenoid with 900 turns per meter and current \( 3.5 \, \text{A} \) has a core with \( \mu_r = 150 \). What is \( B \) inside? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).