NEET Magnetism and Matter — Set 13

Question 1

A magnetic field line pattern that forms closed loops entirely within a material is most likely observed in:

Accepted Answer

In a toroid, magnetic field lines are confined within the core, forming closed loops due to the circular symmetry and the current in the windings. This contrasts with bar magnets or solenoids, where field lines extend externally.

Question 2

A material has $ B = 0.28 \, \text{T} $ and $ M = 2.0 \times 10^5 \, \text{A m}^{-1} $. What is $ 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 = 0.28 \, \text{T} $, $ M = 2.0 \times 10^5 \, \text{A m}^{-1} $, $ \mu_0 = 4\pi \times 10^{-7} $. $ \frac{B}{\mu_0} = \frac{0.28}{4\pi \times 10^{-7}} \approx 2.228 \times 10^5 \, \text{A m}^{-1} $. $ H = 2.228 \times 10^5 - 2.0 \times 10^5 = 2.28 \times 10^4 \, \text{A m}^{-1} $.

Question 3

The magnetic potential energy of a dipole with $ m = 0.5 \, \text{A m}^2 $ in a field $ B = 0.3 \, \text{T} $ at $ 0^\circ $ is:

Accepted Answer

$ U_m = -m B \cos\theta $. Given: $ m = 0.5 \, \text{A m}^2 $, $ B = 0.3 \, \text{T} $, $ \theta = 0^\circ $, $ \cos 0^\circ = 1 $. Substitute: $ U_m = -0.5 \times 0.3 \times 1 = -0.15 \, \text{J} $.

NEET Physics: Magnetism and Matter — Practice Set 13

Q1. A magnetic field line pattern that forms closed loops entirely within a material is most likely observed in:

Q2. A material has \( B = 0.28 \, \text{T} \) and \( M = 2.0 \times 10^5 \, \text{A m}^{-1} \). What is \( H \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q3. The magnetic potential energy of a dipole with \( m = 0.5 \, \text{A m}^2 \) in a field \( B = 0.3 \, \text{T} \) at \( 0^\circ \) is:

Q4. A material with \( B = 0.66 \, \text{T} \) and \( H = 4500 \, \text{A m}^{-1} \) has \( M \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q5. A bar magnet with \( m = 3.5 \, \text{A m}^2 \) is at \( 0.6 \, \text{m} \) along its axis. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q6. A bar magnet with \( m = 1.2 \, \text{A m}^2 \) produces a field at \( 0.3 \, \text{m} \) on its equatorial line. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q7. The magnetic field inside a material becomes zero when:

Q8. A magnetic dipole in a non-uniform field experiences a net force because:

Q9. A dipole with \( m = 0.2 \, \text{A m}^2 \) in \( B = 0.5 \, \text{T} \) at \( 90^\circ \) has torque:

Q10. The magnetic field contribution \( B_m \) due to a material with \( M = 1.2 \times 10^5 \, \text{A m}^{-1} \) is: (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).