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Two infinitely long parallel conducting plates having surface charge densities +σ and -σ respectively, are separated by a small distance. The medium between the plates is vacuum. If 
is the dielectric permittivity of vacuum, then the electric field in the region between the plates is
|
(a) 0 volts/meter |
(b) |
(c) |
(d) |
Antimony and bismuth are usually used in a thermocouple, because
|
(a) Negative thermal e.m.f. produced |
(b) Constant thermal e.m.f. produced |
|
(c) Lower thermal e.m.f. produced |
(d) Higher thermal e.m.f. produced |
Three equal capacitors, each with capacitance C are connected as shown in figure. Then the equivalent capacitance between A and B is
|
(a) C |
(b) 3C |
(c) |
(d) |
If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in 4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm
|
(a) In 8 minutes |
(b) In 12 minutes |
(c) In 16 minutes |
(d) In 20 minutes |
A lamp emits monochromatic green light uniformly in all directions. The lamp is 3% efficient in converting electrical power to electromagnetic waves and consumes 100W of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of 10m from the lamp will be
|
(a) 1.34 V/m |
(b) 2.68 V/m |
(c) 5.36 V/m |
(d) 9.37 V/m |
In 
nucleus, there are
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(a) 138 protons and 88 neutrons |
(b) 138 neutrons and 88 protons |
|
(c) 226 protons and 88 electrons |
(d) 226 neutrons and 138 electrons |
An electron changes its position from orbit n = 4 to the orbit n = 2 of an atom. The wavelength of the emitted radiation’s is (R = Rydberg’s constant)
(a) 
|
(b) 
|
(c) 
|
(d) 
|
