MCQ
In an atom, electrons revolve around the nucleus. This gives rise to:
- AOnly electric field.
- BOnly magnetic field.
- CBoth electric and magnetic fields.
- DNone of the above.
Explanation:
When a charge electron starts to move, electric current generates and this electric current generates magnetic field, a charge at rest also can generate electric field.
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An achromatic combination of lenses is formed by joining
|
(a) 2 convex lenses |
(b) 2 concave lenses |
|
(c) 1 convex lens and 1 concave lens |
(d) Convex lens and plane mirror |
In order to coincide the parabolas formed by singly ionised ions in one spectrograph and doubly ionized ions in the other Thomson’s mass spectrograph, the electric fields and magnetic fields are kept in the ratios 1 : 2 and 3 : 2 respectively. Then the ratio of masses of the ions is
|
(a) 3 : 4 |
(b) 1 : 3 |
(c) 9 : 4 |
(d) None of these |
If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately
|
(a) 60% |
(b) 65% |
(c) 70% |
(d) 75% |
Equipotential surfaces associated with an electric field which is increasing in magnitude along the x-direction are
|
(a) Planes parallel to yz-plane |
|
(b) Planes parallel to xy-plane |
|
(c) Planes parallel to xz-plane |
|
(d) Coaxial cylinders of increasing radii around the x-axis |