NEET Magnetism and Matter — Set 10

Question 1

When a magnetic dipole is placed perpendicular to a uniform magnetic field, the torque acting on it is maximum because:

Accepted Answer

The torque on a magnetic dipole is given by $ \tau = m B \sin\theta $. It reaches its maximum value when $ \sin\theta = 1 $, which occurs at $ \theta = 90^\circ $ (perpendicular orientation), as the cross product $ m \times B $ is greatest when the angle between the dipole moment and field is 90 degrees.

Question 2

The magnetic field lines inside a bar magnet run from:

Accepted Answer

Magnetic field lines form closed loops, exiting the north pole and entering the south pole externally. Inside a bar magnet, they run from the south pole to the north pole to complete the loop, consistent with the convention of field direction from north to south outside.

Question 3

A dipole with $ m = 0.4 \, \text{A m}^2 $ in a field $ B = 0.3 \, \text{T} $ at $ 0^\circ $ has potential energy:

Accepted Answer

$ U_m = -m B \cos\theta $. Given: $ m = 0.4 \, \text{A m}^2 $, $ B = 0.3 \, \text{T} $, $ \theta = 0^\circ $, $ \cos 0^\circ = 1 $. $ U_m = -0.4 \times 0.3 \times 1 = -0.12 \, \text{J} $.

NEET Physics: Magnetism and Matter — Practice Set 10

Q1. When a magnetic dipole is placed perpendicular to a uniform magnetic field, the torque acting on it is maximum because:

Q2. The magnetic field lines inside a bar magnet run from:

Q3. A dipole with \( m = 0.4 \, \text{A m}^2 \) in a field \( B = 0.3 \, \text{T} \) at \( 0^\circ \) has potential energy:

Q4. The magnetic potential energy of a dipole with \( m = 0.9 \, \text{A m}^2 \) in a field \( B = 0.2 \, \text{T} \) at \( 90^\circ \) is:

Q5. A material with \( \mu_r = 300 \) and \( H = 600 \, \text{A m}^{-1} \) has \( B \): (Take \( \mu_0 = 4\pi \times 10^{-7} \, \text{T m A}^{-1} \)).

Q6. A material with \( \chi = -1 \) and \( \mu_r = 0 \) is classified as:

Q7. A material loses its magnetic properties when heated beyond a certain temperature because:

Q8. A magnetic dipole of moment \( 0.8 \, \text{A m}^2 \) is in a uniform field of \( 0.5 \, \text{T} \) at \( 45^\circ \). What is the torque on it?

Q9. The alignment of a magnetic dipole in a uniform field results in:

Q10. A magnetic dipole with \( m = 0.3 \, \text{A m}^2 \) in a field \( B = 0.4 \, \text{T} \) at \( 90^\circ \) has potential energy: