Magnetic field of a short magnet at a distance lm on axial line is 1 oersted at a distance 2 m on the same line the intensity in oersted is

• 0.75

• 0.125

• 0.25

• 0.5

The ratio of magnetic moments of two short magnets which give null deflection in tan B position at 12 cm and 18 cm from the centre of a deflection magnetometer is

• 4:9

• 27:8

• 2:3

• 8:27

The distance between the poles of horse shoe magnet is 10 cm and its pole strength is 10⁴ A. The magnetic field induction at point P mid-way between the poles is

• $8\times {10}^{-9} \mathrm{tesla}$

• 4×10^-19 tesla

• 2×10^-9 tesla

• zero

If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by ${\mathrm{\mu }}_{ \mathrm{d} }, {\mathrm{\mu }}_{ \mathrm{p}} \mathrm{and} {\mathrm{\mu }}_{ \mathrm{f}}$  respectively, then

• ${\mathrm{\mu }}_{ \mathrm{d}} \ne 0 \mathrm{and} {\mathrm{\mu }}_{ \mathrm{f} }\ne 0$

• ${\mathrm{\mu }}_{\mathrm{p}}= 0 \mathrm{and} {\mathrm{\mu }}_{ \mathrm{f}} \ne 0$

• ${\mathrm{\mu }}_{ \mathrm{d}} = 0 \mathrm{and} {\mathrm{\mu }}_{ \mathrm{p}} \ne 0$

• ${\mathrm{\mu }}_{ \mathrm{d} }\ne 0, {\mathrm{\mu }}_{ \mathrm{p}} = 0$

A frog can be levitated in magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as

• paramagnetic

• diamagnetic

• ferromagnetic

• anti-ferromagnetic

A magnetic field exerts no force on

• a magnet

• an unmagnetised iron bar

• a moving charge

• stationary charge

An ideal solenoid having 5000 turns/m has an aluminium core and carries a current of 5A. If χ_Al = 2.3 × 10^-5,  then the magnetic field developed at centre will be

• 0.031 T

• 0.048 T

• 0.027 T

• 0.050 T

Assertion:  In water, value of magnetic field decreases. 

Reason:  Water is a diamagnetic substance

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: Magnetic field lines are continuous and closed. 

Reason:  Magnetic monopole does not exist

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false

30.

The temperature of transition from ferromagnetic property to paramagnetic property is called

• Transition temperature

• Critical temperature

• Curie temperature

• Triplet temperature