MCQ
A magnetic field exerts no force on:
- AA magnet
- BAn unmagnetised iron bar
- CA moving charge
- DStationary charge
Explanation:
Moving charge can develop magnetic field and also experience the magnetic field.
But stationary charge do no have the ability to develop or experience magnetic field from the other magnetic fields.
Because moving charge gives rise to current which is responsible for the magnetic effects.
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Refractive index of air is 1.0003. The correct thickness of air column which will have one more wavelength of yellow light (6000 Å) than in the same thickness in vacuum is
|
(a) 2 mm |
(b) 2 cm |
(c) 2 m |
(d) 2 km |
When one of the slits of Young’s experiment is covered with a transparent sheet of thickness 4.8 mm, the central fringe shifts to a position originally occupied by the 30th bright fringe. What should be the thickness of the sheet if the central fringe has to shift to the position occupied by 20th bright fringe
|
(a) 3.8 mm |
(b) 1.6 mm |
(c) 7.6 mm |
(d) 3.2 mm |
The electric intensity E, current density j and specific resistance k are related to each other by the relation
|
(a) E = j/k |
(b) E = jk |
(c) E = k/j |
(d) k = jE |
The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is
|
(a) 1/2 |
(b) 2/137 |
(c) 1/137 |
(d) 1/237 |
When the wavelength of light coming from a distant star is measured it is found shifted towards red. Then the conclusion is
|
(a) The star is approaching the observer |
(b) The star recedes away from earth |
|
(c) There is gravitational effect on the light |
(d) The star remains stationary |
An e.m.f. of 12 volts is induced in a given coil when the current in it changes at the rate of 48 amperes per minute. The self inductance of the coil is
|
(a) 0.25 henry |
(b) 15 henry |
(c) 1.5 henry |
(d) 9.6 henry |
One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is
|
(a) 0.4 |
(b) 0.8 |
(c) 1.2 |
(d) 1.6 |
A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black: