A radioactive sample at any instant has its disintegration rate 5000 disintegration per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is
|
(a) 0.8 In 2 |
(b) 0.4 In 2 |
(c) 0.2 In 2 |
(d) 0.1 In 2 |
(b) 0.4 In 2
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A charged particle is moving with velocity v in a magnetic field of induction B. The force on the particle will be maximum when
|
(a) v and B are in the same direction |
(b) v and B are in opposite directions |
|
(c) v and B are perpendicular |
(d) v and B are at an angle of 45° |
If two lenses of +5 diopters are mounted at some distance apart, the equivalent power will always be negative if the distance is
|
(a) Greater than 40 cm |
(b) Equal to 40 cm |
|
(c) Equal to 10 cm |
(d) Less than 10 cm |
The maximum focal length of the eye-lens of a person is greater than its distance from the retina. The eye is:
A simple pendulum of period T has a metal bob which is negatively charged. If it is allowed to oscillate above a positively charged metal plate, its period will
|
(a) Remains equal to T |
(b) Less than T |
|
(c) Greater than T |
(d) Infinite |
In a copper voltameter, mass deposited in 6 minutes is m gram. If the current-time graph for the voltameter is as shown here, then the E.C.E of the copper is
|
(a) m / 5 |
(b) m / 300 |
(c) 5 m |
(d) m / 18000 |
Two wires of resistance R1 and R2 have temperature coefficient of resistance 
and 
, respectively. These are joined in series. The effective temperature coefficient of resistance is
|
(a) |
(b) |
(c) |
(d) |
