CBSE
Multiple Choice QuestionsA bar magnet of length l and magnetic dipole moment M is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be
M
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 bar magnet has a coercivity of 4 x 103 Am-1. It is placed inside a solenoid of length 12 cm having 60 turns in order to demagnetise it. The amount of current that should be passed through the solenoid is
16 A
8 A
4 A
2 A
The magnetic moment of a short bar magnet is 4 Am2 . The magnetic induction at a point 10 cm away from its mid point on axial line is B1 , and on the equatorial line is B2 , then
B1 = 8 × 10-4 T , B2 = 4 × 10-4 T
B1 = 2 × 10-4 T , B2 = 1 × 10-4 T
B1 = 10 × 10-4 T , B2 = 5 × 10-4 T
B1 = 6 × 10-4 T , B2 = 3 × 10-4 T
A straight conductor of length 0.4 m is moved with a speed of 7 m/s perpendicular to the magnetic field of intensity of 0.9 Wb/m2. The induced emf across the conductor will be
7.25 V
5.54 V
1.25 V
2.52 V
The figure illustrates how the flux density B inside a sample of demagnetised ferromagnetic material varies with the magnetic flux density B0 , in which the sample is kept. For the sample to be suitable for making a permanent magnet, then which statement is true for this?
OQ should be large, OR should be small
both OQ and OR should be large
OQ should be small and OR should be large
both OQ and OR should be small
A place where the vertical component of the earth's magnetic field is zero has angle of dip is
45°
90°
0°
60°
Magnetic field intensify at the centre of coil of 50 turns, 0.5 m radius and carrying a current of 2A, is
5x 10-5 T
3 x 10-5 T
1.25 × 10-4 T
0.5 x 10-5 T
If the earth field induction at a place is 0.36 gauss and the angle of dip is 60°, the horizontal and vertical components of the field will be respectively
0.18 gauss, 0.18 gauss
0.98 gauss, 0.9 gauss
1.08 gauss, and 1.08 gauss
1.07 gauss, 0.11 gauss
The value of angle of dip is zero at the magnetic equator because on it
V and H are equal
the value of V is zero
the value of H is zero
the value of V is infinity
