Class 12 Magnetism and Matter worksheet

Sample questions

Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.

Section A · multiple choice

1. 1.

   A bar magnet of magnetic moment 2 A m² makes 150° with a uniform field of 6 × 10⁻² T. The torque on it is:

   1. 6 × 10⁻⁴ N m
   2. 0.12 N m
   3. 0 N m
   4. 0.06 N m

   Answer

   (d) 0.06 N m

   τ = mB sin θ

2. 2.

   The magnetic field 20 cm from the centre of a short bar magnet of moment 9 A m², on its axis, is: (μ₀ = 4π × 10⁻⁷ T m/A)

   1. 1.125 × 10⁻⁴ T
   2. 2.25 × 10⁻⁶ T
   3. 2.25 × 10⁻⁴ T
   4. 4.5 × 10⁻³ T

   Answer

   (c) 2.25 × 10⁻⁴ T

   B = (μ₀/4π) × 2m/r³

3. 3.

   A magnet of moment 2 A m² makes 90° with a field of 2 × 10⁻² T. Its potential energy is:

   1. 0.04 J
   2. −0.02 J
   3. −0.04 J
   4. 0 J

   Answer

   (d) 0 J

   U = −mB cos θ

Section B · short answer

1. 4.

   A coil of 226 turns and area 26 cm² carries 1 A. Find its magnetic moment and the largest torque on it in a field of 9 × 10⁻² T.

   Answer

   0.5876 A m²; 0.052884 N m

   m = NIA; τmax = mB

2. 5.

   A short bar magnet has moment 8 A m². Find the field 5 cm from its centre (a) on its axis, (b) on its equatorial line. (μ₀ = 4π × 10⁻⁷ T m/A)

   Answer

   (a) 0.0128 T; (b) 6.4 × 10⁻³ T

   axis: 2m/r³ × 10⁻⁷; equator: m/r³ × 10⁻⁷

Section C · long answer

1. 6.

   A short bar magnet of moment 1 A m² lies along the x-axis with its centre at the origin. Find the field at (20 cm, 0) and at (0, 20 cm), and the ratio of the two. (μ₀ = 4π × 10⁻⁷ T m/A)

   Answer

   2.5 × 10⁻⁵ T along the axis; 1.25 × 10⁻⁵ T, opposite to the moment; ratio 2 : 1

   B(axis) = 2m/r³ × 10⁻⁷, B(equator) = m/r³ × 10⁻⁷

Fresh sheets for your child

In the app, every Magnetism and Matter sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.

Coming soon for Android and iPhone.

More Class 12 Physics