NEET Magnetism and Matter — Set 7

Question 1

A bar magnet with original $ m = 1.4 \, \text{A m}^2 $ is cut along its length into two equal parts. What is $ m $ of each part?

Accepted Answer

When cut along its length, each part typically has half the original magnetic moment in standard problems. Given: $ m = 1.4 \, \text{A m}^2 $. Each part: $ m' = \frac{1.4}{2} = 0.7 \, \text{A m}^2 $.

Question 2

A material with susceptibility $ \chi = -3 \times 10^{-5} $ has a relative permeability $ \mu_r $ of:

Accepted Answer

$ \mu_r = 1 + \chi $. Given: $ \chi = -3 \times 10^{-5} $. Substitute: $ \mu_r = 1 - 3 \times 10^{-5} = 0.99997 $.

Question 3

A bar magnet produces a field of $ 8 \times 10^{-6} \, \text{T} $ at $ 0.4 \, \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 = 8 \times 10^{-6} \, \text{T} $, $ r = 0.4 \, \text{m} $, $ \frac{\mu_0}{4\pi} = 10^{-7} $. $ m = \frac{8 \times 10^{-6} \times (0.4)^3}{10^{-7}} = \frac{8 \times 10^{-6} \times 0.064}{10^{-7}} = 5.12 \, \text{A m}^2 $.

NEET Physics: Magnetism and Matter — Practice Set 7

Q1. A bar magnet with original \( m = 1.4 \, \text{A m}^2 \) is cut along its length into two equal parts. What is \( m \) of each part?

Q2. A material with susceptibility \( \chi = -3 \times 10^{-5} \) has a relative permeability \( \mu_r \) of:

Q3. A bar magnet produces a field of \( 8 \times 10^{-6} \, \text{T} \) at \( 0.4 \, \text{m} \) on its equatorial line. What is its magnetic moment? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q4. A bar magnet with \( m = 1.8 \, \text{A m}^2 \) is at \( 0.6 \, \text{m} \) along its axis. What is \( B \)? (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q5. The magnetic field contribution \( B_m \) due to a material with \( M = 2.8 \times 10^5 \, \text{A m}^{-1} \) is: (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q6. A bar magnet of magnetic moment \( 0.5 \, \text{A m}^2 \) is placed at a distance of \( 20 \, \text{cm} \) from its center along its axis. Calculate the magnetic field \( B \) at that point. (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q7. A material with susceptibility \( \chi = -8 \times 10^{-5} \) has a relative permeability \( \mu_r \) of:

Q8. A dipole with \( m = 0.8 \, \text{A m}^2 \) in a field \( B = 0.5 \, \text{T} \) at \( 45^\circ \) has potential energy:

Q9. A solenoid with 700 turns per meter carries a current of \( 2 \, \text{A} \). What is the magnetic intensity \( H \) inside?

Q10. The net magnetic flux through a closed surface surrounding a toroid with current is: