The 6563 ?A Hα line emitted by hydrogen in a star is found to be red-shifted by 15 A?. Estimate the speed with which the star is receding from the Earth.

1) 68.6×10⁵ms−1
2) 2.86×10⁵ms⁻¹
3) 6.86×10⁵ms−1
4) 1.86×10⁵ms−1

A circuit has a self-inductance of 1H and carries a current of 2A. To prevent sparking, when the circuit is switched off, a capacitor which can withstand 400V is used. The least capacitance of capacitor connected across the switch must be equal to

1) 50μF

2) 25μF

3) 100μF

4) 12.5μF

Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion

1) depends on R and not v
2) is independent of both R and v
3) depends on both R and v
4) depends on v and not on R

 An isolated conductor will become polarized (in terms of charge) when:

(1) it is touched by a charged object.

(2) it is warmed.

(3) it is brought close to (but not touching) a charged object.

(4) it is charged with a power supply

A temporary magnet should be made from
 
 (1) Copper
 (2) Steel
 (3) Tin
 (4) Aluminum

If we double the radius of a coil keeping the current through it unchanged, then the magnetic field at any point at a large distance from the center becomes approximately,
1. Half
2. Same
3. Double
4. Four - times

Just as electricity is supplied at 220 V for domestic use in India, It is supplied at 110 V in U.S. A. If resistance of 60 W bulb for use in India is R, that of a 60 W bulb for use in U.S.A. will be:

(1) R
(2) 2R
(3) R/4
(4) R/2

 The electirc field strength at a distance rr from the centre of a charged sphere of radius r is E. If r > R, how much work will be done in bringing a test charge q₀ from infinity to that point, is

(1) q₀RE  
(2) 1/2 q₀RE        
(3) q₀ r E       
(4) 1/2 q₀ r E

A quill tube contains a mercury column of length 19 cm. The length of air column is 24 cm when it is held vertically. On inverting it with its open end downwards the length of air column will be_______cm. (atmospheric pressure = 76 cm of Hg)

1) 20 cm
2) 30 cm
3) 40 cm
4) 35 cm

The kinetic energy of a particle in S.H.M. is 9J when it passes through the mean position. If its mass is 2 kg and the amplitude is 1m, the time period is:

1) 2.09 s
2) 3.14 s
3) 2.57 s
4) 1.79 s