### Physics - Magnetism and Matter

#### Question - 1

A current of 2 A is passed in a coil of radius 0.5 m and number of turns in it is 20. The magnetic moment of the coil is

• A 0.314 A-m2
• B 3.14 A-m2
• C 314 A-m2
• D 31.4 A-m2

#### Question - 2

A magnet of moment m is lying in a magnetic field of induction B. W1 is the work done in turning it from 00 to 60o and W2 is the work done in turning it from 30o to 90o . Then

• A ${ W }_{ 2 }={ W }_{ 1 }$
• B ${ W }_{ 2 }=\frac { { W }_{ 1 } }{ 2 }$
• C ${ W }_{ 2 }=2{ W }_{ 1 }$
• D ${ W }_{ 2 }=\sqrt { 3 } { W }_{ 1 }$

#### Question - 3

A toroid of n turn, mean radius R and cross- sectional radius a carries current I. It is placed on a horizontal table taken as XY-plane. Its magnetic moment m

• A is non-zero and points in the Z direction by symmetry
• B points along the axis of the toroid
• C is zero
• D is pointing radially outwards

#### Question - 4

The inner and the outer radii of a toroid are 9 cm and 11 cm respectively and the number of turns in it is 3140. A magnetic field of 2.5 T is produced in it when a current of 0.5 A is passed in it. The permeability of core material is (in H/m)

• A 10-1
• B 10-2
• C 10-3
• D 10-4

#### Question - 5

The magnetic field of the earth can be modelled by that of a point dipole placed at the centre of the earth. The dipole axis makes an angle of 11.3o with the axis of the earth. At Mumbai, declination is nearly zero. Then,

• A the declination varies between 11.3o W to 11.3oE
• B the least declination is 0o
• C the plane defined by dipole axis and earth axis passes through greenwich
• D declination averaged over the earth always be negative

#### Question - 6

The horizontal component of the earth's magnetic field at any place is 0.36X10-4 Wb/m2 . If the angle of dip at that place is 60o , then the value of vertical component of the earth's magnetic field will be (in Wb/m2)

• A 0.12X10-4
• B 0.24X10-4
• C 0.40X10-4
• D 0.622X10-4

#### Question - 7

The intensity of magnetisation (I) depends on magnetising field (H)

• A $I\propto H$
• B $I\propto \frac { 1 }{ { H }^{ 2 } }$
• C $I\propto \frac { 1 }{ { H } }$
• D $I\propto { H }^{ 2 }$

#### Question - 8

The dipole moment of each molecule of a paramagnetic gas is 1.5X10-23 A-m2. The temperature of gas is 27o C and the number of molecules per unit volume in it is 2.0X1026 m-3 m-3 . The maximum possible intensity of magnetisation in the gas will be (in A/m)

• A 3X103
• B 4X10-3
• C 5X105
• D 6X10-4

#### Question - 9

The magnetic moment of a magnet of mass 75 g is 9X10-7 A-m2. If the density of the material of magnet is 7.5X103 kg/m3 , then intensity of magnetisation will be

• A 0.9 A/m
• B 0.09 A/m
• C 9 A/m
• D 90 A/m

#### Question - 10

Steel is a

• A non-magnetic
• B paramagnetic
• C diamagnetic
• D ferromagnetic