Explanation:
Energy gaps between the highest band and the lowest empty bands is lowest in metals, moderate in semi conductors and very high in insulators. This suggests us that:
Element A must be a metal, element C must be an insulator and element B and D can be semiconductors.
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Deviation of 5° is observed from a prism whose angle is small and whose refractive index is 1.5. The angle of prism is
|
(a) 7.5° |
(b) 10° |
(c) 5° |
(d) 3.3° |
The chemical equivalent of silver is 108. If the current in a silver voltameter is 2 Amp., the time required to deposit 27 grams of silver will be
|
(a) 8.57 hrs |
(b) 6.70 hrs |
(c) 3.35 hrs |
(d) 12.50 hrs |
Assertion : If two long wires, hanging freely are connected to a battery in series, they come closer to each other.
Reason : Force of attraction acts between the two wires carrying current.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
The ratio of the energies of the hydrogen atom in its first to second excited state is
|
(a) 1/ 4 |
(b) 4/9 |
(c) 9/ 4 |
(d) 4 |
A device which converts electrical energy into mechanical energy is
|
(a) Dynamo |
(b) generator |
(c) Electric motor |
(d) Induction coil |
A thin equiconvex lens is made of glass of refractive index 1.5 and its focal length is 0.2 m, if it acts as a concave lens of 0.5 m focal length when dipped in a liquid, the refractive index of the liquid is
|
(a) |
(b) |
(c) |
(d) |
A hot electric iron has a resistance of 80 Ω and is used on a 200 V source. The electrical energy spent, if it is used for two hours, will be
|
(a) 8000 Wh |
(b) 2000 Wh |
(c) 1000 Wh |
(d) 800 Wh |
