NEET Magnetism and Matter — Set 5

Question 1

A material that completely expels magnetic field lines from its interior when cooled to a very low temperature is likely to be:

Accepted Answer

Superconductors exhibit perfect diamagnetism (Meissner effect) when cooled below their critical temperature, expelling all magnetic field lines from their interior. This is due to induced surface currents that cancel the internal field, a property unique to superconductors.

Question 2

The fact that magnetic field lines do not start or end at any point is a direct result of:

Accepted Answer

Magnetic field lines form closed loops because there are no magnetic monopoles; every field line exiting a region must re-enter, ensuring continuity, as dictated by the absence of isolated magnetic charges in nature.

Question 3

A bar magnet produces a field of $ 7 \times 10^{-6} \, \text{T} $ at $ 0.5 \, \text{m} $ on its equatorial line. What is its magnetic moment? (Take $ \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} $).

Accepted Answer

$ B = \frac{\mu_0}{4\pi} \frac{m}{r^3} $, so $ m = \frac{B r^3}{\frac{\mu_0}{4\pi}} $. Given: $ B = 7 \times 10^{-6} \, \text{T} $, $ r = 0.5 \, \text{m} $, $ \frac{\mu_0}{4\pi} = 10^{-7} $. $ m = \frac{7 \times 10^{-6} \times (0.5)^3}{10^{-7}} = \frac{7 \times 10^{-6} \times 0.125}{10^{-7}} = 8.75 \, \text{A m}^2 $.

NEET Physics: Magnetism and Matter — Practice Set 5

Q1. A material that completely expels magnetic field lines from its interior when cooled to a very low temperature is likely to be:

Q2. The fact that magnetic field lines do not start or end at any point is a direct result of:

Q3. A bar magnet produces a field of \( 7 \times 10^{-6} \, \text{T} \) at \( 0.5 \, \text{m} \) on its equatorial line. What is its magnetic moment? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q4. A material that weakly repels magnetic field lines and has a susceptibility slightly less than zero is classified as:

Q5. A bar magnet is cut transversely into two equal parts. If the original magnetic moment was \( 0.6 \, \text{A m}^2 \), what is the magnetic moment of each part?

Q6. A bar magnet with magnetic moment \( 1.2 \, \text{A m}^2 \) is placed at a distance of \( 0.4 \, \text{m} \) along its axis. What is the magnetic field \( B \) at that point? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q7. A bar magnet with original \( m = 2.4 \, \text{A m}^2 \) is cut transversely into two equal parts. What is \( m \) of each part?

Q8. A material has \( B = 0.5 \, \text{T} \) and \( M = 2 \times 10^5 \, \text{A m}^{-1} \). What is \( H \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q9. The magnetic field outside a long solenoid is nearly zero because:

Q10. A bar magnet produces a field of \( 4 \times 10^{-6} \, \text{T} \) at \( 0.2 \, \text{m} \) on its equatorial line. What is its magnetic moment? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).