A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is
|
(a) 1080 |
(b) 2430 |
(c) 3240 |
(d) 4860 |
(a) 1080
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
In an induction coil, the secondary e.m.f. is
|
(a) Zero during break of the circuit |
|
(b) Very high during make of the circuit |
|
(c) Zero during make of the circuit |
|
(d) Very high during break of the circuit |
A proton is accelerated through 50,000 V. will increase Its energy by
|
(a) 5000 eV |
(b) 8 |
(c) 5000 J |
(d) 50,000 J |
An object is placed 40 cm from a concave mirror of focal length 20 cm The image formed is
|
(a) Real, inverted and same in size |
(b) Real, inverted and smaller |
|
(c) Virtual, erect and larger |
(d) Virtual, erect and smaller |
In a thermocouple, the temperature that does not depend on the temperature of the cold junction is called
|
(a) Neutral temperature |
(b) Temperature of inversion |
|
(c) Both the above |
(d) None of the above |
A piece of fuse wire melts when a current of 15 ampere flows through it. With this current, if it dissipates 22.5 W, the resistance of fuse wire will be
|
(a) Zero |
(b) 10 Ω |
(c) 1 Ω |
(d) 0.10 Ω |
Best neutron moderator is
|
(a) Berillium oxide |
(b) Pure water |
(c) Heavy water |
(d) Graphite |
A parallel plate capacitor of area A, plate separation d and capacitance C is filled with three different dielectric materials having dielectric constants 
and 
as shown. If a single dielectric material is to be used to have the same capacitance C in this capacitor, then its dielectric constant k is given by
(a) 
|
(b) 
|
|
(c) k = |
(d) |
