Two equal and unlike poles placed 5 cm apart in air attract each other with a force of 14 . 4 × 10 - 4 N . How far from each other should they be placed so that the force of attraction will be 1 . 6 × 10 - 4 N ?

Distance between magnetic pole, r = 5 cm The force of attraction between poles, F 1 = 14 . 4 × 10 - 4 N The new force of attraction between poles, F 2 = 1 . 6 × 10 - 4 N We know the force of attraction or repulsion between two poles is given by F = μ 0 4 π . m 1 m 2 r 2 , i.e. F ∝ 1 r 2 ∴ F 1 F 2 = r 2 2 r 1 2 ⇒ r 2 = F 1 F 2 . r 1 = 14 .4 × 10 - 4 1 .6 × 10 - 4 × 5 × 10 - 2 = 0 .15 m

E M B I B E

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 12

EASY

12th CBSE

IMPORTANT

Earn 100

Derive an expression for the torque on a magnetic dipole placed in a magnetic field and hence define magnetic dipole moment.

Important Questions on Magnetism

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Problems For Practice>Q 1

Two magnetic south poles are located

4.0 cm

apart. If the poles of each magnet have a strength of

8.0 Am

and are

20.0 cm

apart, find the force exerted by one south pole on the other.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Problems For Practice>Q 2

Two equal and unlike poles placed

5 cm

apart in air attract each other with a force of

14.4 \times 10^{- 4} N

. How far from each other should they be placed so that the force of attraction will be

1.6 \times 10^{- 4} N

?

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 19

Compare the magnetic fields of a bar magnet and current carrying solenoid.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 20

Explain with the help of diagram (i) magnetic declination and (ii) angle of dip at a place. In what direction will a compass needle point when kept at the (i) poles and (ii) equator?

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 36

Define the terms retentivity and coercivity.

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12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 43

Out of the following, identify the materials which can be classified as diamagnetic:
1.Aluminium

2. Bismuth

3. Copper

4. Sodium
Write one property to distinguish between paramagnetic and diamagnetic materials.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 6

A small compass needle of magnetic moment

' m'

is free to turn about an axis perpendicular to the direction of uniform magnetic field

' B'

. The moment of inertia of the needle about the axis is

' I'

. The needle is slightly disturbed from its stable position and then released. Prove that it executes simple harmonic motion. Hence deduce the expression for its time period.

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 5 - Magnetism>Text Based Exercises>Q 7

An electron in the ground state of Hydrogen atom is revolving in a circular orbit of radius