- 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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A 4 mF condenser is charged to 400 V and then its plates are joined through a resistance. The heat produced in the resistance is
|
(a) 0.16 J |
(b) 0.32 J |
(c) 0.64 J |
(d) 1.28 J |
Basically, the product modulator is
|
(a) An amplifier |
(b) A mixer |
|
(c) A frequency separator |
(d) A phase separator |
Radius of first Bohr orbit is r. What is the radius of 2nd Bohr orbit?
| (a) 8r | (b) 2r | (c) 4r |
(d) 2 |
A voltmeter essentially consists of
|
(a) A high resistance, in series with a galvanometer |
|
(b) A low resistance, in series with a galvanometer |
|
(c) A high resistance in parallel with a galvanometer |
|
(d) A low resistance in parallel with a galvanometer |
A circular coil of radius 4 cm has 50 turns. In this coil a current of 2 A is flowing. It is placed in a magnetic field of 0.1
. The amount of work done in rotating it through 180° from its equilibrium position will be
|
(a) 0.1 J |
(b) 0.2 J |
(c) 0.4 J |
(d) 0.8 J |
The electric field between the plates of a parallel plate capacitor when connected to a certain battery I . If the space between the plates of the capacitor is filled by introducing a material of dielectric constant K without disturbing the battery connections, the field between the plates shall be
|
(a) |
(b) |
(c) |
(d) None of the above |
A biconvex lens forms a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then the image would
|
(a) Disappear |
|
(b) Remain as real image still |
|
(c) Be virtual and of the same size as the object |
|
(d) Suffer from aberrations |
Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be
|
(a) 20 minutes |
(b) 40 minutes |
(c) 30 minutes |
(d) 25 minutes |