Solution:
Key concept: As we know whenever the number of magnetic lines of force (magnetic flux) passing through a circuit changes, an e.m.f is produced in the circuit called induced e.m.f. The induced e.m.f persists only as long as there is a change or cutting of flux.
In this problem, magnetic flux linked with the isolated coil changes when the coil is placed in the region of a time varying magnetic field, the coil moving in a constant magnetic field or in time varying magnetic field.
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The work done in rotating a magnet of magnetic moment 2 A-m2 in a magnetic field of 5 × 10–3 T from the direction along the magnetic field to opposite direction to the magnetic field, is
|
(a) Zero |
(b) 2 × 10–2 J |
(c) 10–2 J |
(d) 10 J |
To make a PN junction conducting
|
(a) The value of forward bias should be more than the barrier potential |
|
(b) The value of forward bias should be less than the barrier potential |
|
(c) The value of reverse bias should be more than the barrier potential |
|
(d) The value of reverse bias should be less than the barrier potential |
The length of the optical path of two media in contact of length 
and 
of refractive indices 
and 
respectively, is
(a) 
|
(b) 
|
(c) |
(d) |
A rectangular coil 20 cm × 20 cm has 100 turns and carries a current of 1 A. It is placed in a uniform magnetic field B = 0.5 T with the direction of magnetic field parallel to the plane of the coil. The magnitude of the torque required to hold this coil in this position is
|
(a) Zero |
(b) 200 N-m |
(c) 2 N-m |
(d) 10 N-m |
In Young's double slit experiment, the distance between the slits is 1 mm and that between slit and screen is 1 meter and 10th fringe is 5 mm away from the central bright fringe, then wavelength of light used will be
|
(a) 5000 Å |
(b) 6000 Å |
(c) 7000 Å |
(d) 8000 Å |
The intensity of gamma radiation from a given source is I. On passing through 36 mm of lead, it is reduced to 
. The thickness of lead which will reduce the intensity to 
will be
|
(a) 18 mm |
(b) 12 mm |
(c) 6 mm |
(d) 9 mm |
If the speed of light in vacuum is C m/sec, then the velocity of light in a medium of refractive index 1.5
|
(a) Is 1.5 × C |
(b) Is C |
|
(c) Is |
(d) Can have any velocity |
A finite ladder is constructed by connecting several sections of 2μF,4 μF capacitor combinations as shown in the figure. It is terminated by a capacitor of capacitance C. What value should be chosen for C such that the equivalent capacitance of the ladder between the points A and B becomes independent of the number of sections in between
|
(a) 4μF |
(b) 2 μF |
(c) 18 μF |
(d) 6 μF |
