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Masses of 3 wires of same metal are in the ratio 1 : 2 : 3 and their lengths are in the ratio 3 : 2 : 1. The electrical resistances are in ratio
|
(a) 1 : 4 : 9 |
(b) 9 : 4 : 1 |
(c) 1 : 2 : 3 |
(d) 27 : 6 : 1 |
A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of 1 mm diameter carrying the same current. The strength of magnetic field far away is
|
(a) Twice the earlier value |
(b) Half of the earlier value |
|
(c) Quarter of its earlier value |
(d) Unchanged |
The energy of a photon of light of wavelength 450 nm is
|
(a) 4.4 |
(b) 2.5 |
(c) 1.25 |
(d) 2.5 |
| C-1 (waves) | C-II (Production) |
| (1) Infra-red | P. Rapid vibration of electrons in aerials |
| (2) Radio | Q. Electrons in atoms emit light when they move from higher to lower energy level. |
| (3) Light | R. Klystron valve |
| (4) Microwave | S. Vibration of atoms and molecules |
Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction 
is established inside the coil. If the key (K) is closed, the electrical power developed right after closing the switch is equal to
|
(a) |
(b) |
(c) |
(d) |
Armature current in dc motor will be maximum when
|
(a) Motor has acquired maximum speed |
(b) Motor has acquired intermediate speed |
|
(c) Motor has just started moving |
(d) Motor is switched off |
The electric potential at a point on the axis of an electric dipole depends on the distance r of the point from the dipole as
|
(a) ∝ |
(b) ∝ |
(c) ∝ r |
(d) ∝ |
