﻿ A bar magnet of moment of inertia 9 x 10-5 kg m2 placed in a vibration magnetometer and oscillating in a uniform magnetic field 16π2 × 10-5 T makes 20 oscillations in 15 s. The magnetic moment of the bar magnet is | Magnetism and Matter

## Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

## Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

## Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.

# Magnetism and Matter

#### Multiple Choice Questions

1.

Two short bar magnets of length 1 cm each have magnetic moments 1.20 Am2 and 1.00 Am2 respectively. They are placed on a horizontal table parallel to each other with their N poles pointing towards the South.
They have a common magnetic equator and are separated by a distance of 20.0 cm. The value of the resultant horizontal magnetic induction at the mid - point O of the line joining their centres is close to(Horizontal component of earth’s magnetic induction is 3.6 × 10–5 Wb/m2)

• 3.6 x10-5 Wb/m2

• 2.56 x10-4 Wb/m2

• 3.50  x10-4 Wb/m2

• 3.50  x10-4 Wb/m2

251 Views

2.

Relative permittivity and permeability of a material are εr and µr, respectively. Which of the following values of these quantities are allowed for a diamagnetic material?

• εr = 0.5, µr = 1.5

• εr = 1.5, µr = 0.5

• εr = 0.5, µr = 0.5

• εr = 0.5, µr = 0.5

208 Views

3.

Needles N1, N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will

• attract all three of them

• attract N1 and N2 strongly but repel N3

• attract N1 strongly, N2 weakly and repel N3 weakly

• attract N1 strongly, N2 weakly and repel N3 weakly

166 Views

4.

Two long conductors, separated by a distance d carry current I1 and I2 in the same direction. They exert a force F on each other. Now the current in one of them increased to two times and its direction reversed. The distance is also increased to 3d. The new value of the force between them is

• −2F

• F/3

• −2F/3

• −2F/3

255 Views

5.

The length of a magnet is large compared to its width and breadth. The time period of its width and breadth. The time period of its oscillation in a vibration magnetometer is 2 s. The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together. The time period of this combination will be

• 2 s

• 2/3 s

• 2√3 s

• 2√3 s

700 Views

6.

The materials suitable for making electromagnets should have

• high retentivity and high coercivity

• low retentivity and low coercivity

• high retentivity and low coercivity

• high retentivity and low coercivity

433 Views

# 7.A bar magnet of moment of inertia 9 x 10-5 kg m2 placed in a vibration magnetometer and oscillating in a uniform magnetic field 16π2 × 10-5 T makes 20 oscillations in 15 s. The magnetic moment of the bar magnet is3 A-m2 2 A-m2 4 A-m2 6 A-m2

C.

4 A-m2

Given,

I = 9 × 10-5 kg-m2

B = 16π2 × 10-5 T

T = $\frac{15}{20}$ = 0.75

The time period

8.

Identify the correctly matched pair

• Soft ferromagnetic   —   Alnico

• Hard ferromagnetic   —   Copper

• Paramagnetic   —   Sodium

9.

The ferromagnetic core of electromagnets should have

• high permeability and high retentivity

• high permeability and low retentivity

• low permeability and high retentivity

10.

A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 rads-1. If the horizontal component of earth's magnetic field is 0.2 x 10-4 T, then the emf developed between the ends of the conductor is

• 5 µV

• 5 mV

• 50 µV

• 50 mV