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The average number of prompt neutrons produced per fission of 
is
|
(a) More than 5 |
(b) 3 to 5 |
(c) 2 to 3 |
(d) 1 to 2 |
A sample of radioactive element has a mass of 10 gm at an instant t = 0.The approximate mass of this element in the sample after two mean lives is
|
(a) 2.50 gm |
(b) 3.70 gm |
(c) 6.30 gm |
(d) 1.35 gm |
Which of the following planets have rings around it
|
(a) Uranus |
(b) Mars |
(c) Jupiter |
(d) Saturn |
A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be
|
(a) One fourth |
(b) Halved |
(c) Doubled |
(d) Four times |
Fast neutrons can easily be slowed down by
|
(a) The use of lead shielding |
(b) Passing them through water |
|
(c) Elastic collisions with heavy nuclei |
(d) Applying a strong electric field |
Figure (i) shows a conducting loop being pulled out of a magnetic field with a speed v. Which of the four plots shown in figure (ii) may represent the power delivered by the pulling agent as a function of the speed v
|
(a) a |
(b) b |
(c) c |
(d) d |
A charged particle q is shot towards another charged particle Q which is fixed, with a speed v. It approaches Q upto a closest distance r and then returns. If q were given a speed 2v, the closest distances of approach would be
|
(a) r |
(b) 2r |
(c) r/2 |
(d) r/4 |
Magnetic lines of force due to a bar magnet do not intersect because
|
(a) A point always has a single net magnetic field |
|
(b) The lines have similar charges and so repel each other |
|
(c) The lines always diverge from a single point |
|
(d) The lines need magnetic lenses to be made to intersect |