A magnetic needle vibrates in a vertical plane parallel to the magnetic meridian about a horizontal axis passing through its centre. Its frequency is n. If the plane of oscillation is turned about a vertical axis by 90°C, the frequency of its oscillation in vertical plane will be

n
zero
less than n
more than n

Solution

The net magnetic moment of two identical magnets each of magnetic moment M₀, inclined at 60° with each other is

M ₀
√2 M ₀
√3 M ₀
2 M ₀

Solution

Torques τ₁ and τ₂ are required for a magnetic needle to remain perpendicular to the magnetic fields at two different places. The magnetic fields at those places are B₁ and B₂ respectively; then ratio \(\frac{B_{1}}{B_{2}}\) is

\(\frac{\tau _{2}}{\tau _{1}}\)
\(\frac{\tau _{1}}{\tau _{2}}\)
\(\frac{\tau _{1}+\tau _{2}}{\tau _{1}-\tau _{2}}\)
\(\frac{\tau _{1}-\tau _{2}}{\tau _{1}+\tau _{2}}\)

Solution

The magnetic moment of atomic neon is equal to

zero
¹⁄₂µ_B
µ_B
³⁄₂µ_B

Solution

Magnetic moment is cancelled and µ_net= 0.

A steel wire of length l has a magnetic moment M. It is then bent into a semicircular are. The new magnetic moment is

^M⁄_π
^2M⁄_π
^3M⁄_π
^4M⁄_π

Solution

A watch glass containing some powdered substance is placed between the pole pieces of a magnet. Deep concavity is observed at the centre.The substance in the watch glass is

iron
chromium
carbon
wood

Solution

Iron is ferromagnetic.

A freely suspended magnet oscillates with period T in earth’s horizontal magnetic field. When a bar magnet is brought near it,such that the magnetic field created by bar magnet is in same direction as earth’s horizontal magnetic field, the period decreases to ^T⁄₂. The ratio of the field of the magnet F to the earth’s magnetic field (H) is

1 : 3
1 : 1
3 : 1
9 : 1

Solution

A superconductor exhibits perfect :

ferrimagnetism
ferromagnetism
paramagnetism
diamagnetism

Solution

A superconductor exhibits perfect diamagnetism.

Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the earth’s magnetic field with like poles together. 12 oscillations per minute are made but for unlike poles together only 4 oscillations per minute are executed. The ratio of their magnetic moments is

3 : 1
1 : 3
3 : 5
5 : 4

Solution

Work done in turning a magnet of magnetic moment M by an angle of 90º from the mgnetic meridian is n times the corresponding work done to turn through an angle of 60º,where n is

Solution

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