The most commonly used material for making transistor is
|
(a) Copper |
(b) Silicon |
(c) Ebonite |
(d) Silver |
The most commonly used material for making transistor is
|
(a) Copper |
(b) Silicon |
(c) Ebonite |
(d) Silver |
(b) Silicon
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The critical angle of a medium with respect to air is 45°. The refractive index of medium is
|
(a) 1.41 |
(b) 1.2 |
(c) 1.5 |
(d) 2 |
A certain wire has a resistance R. The resistance of another wire identical with the first except having twice its diameter is
|
(a) 2R |
(b) 0.25 R |
(c) 4R |
(d) 0.5 R |
The effective resistance between points A and B is
|
(a) 10 Ω |
(b) 20 Ω |
|
(c) 40 Ω |
(d) None of the above three values |
If a 30 V, 90 W bulb is to be worked on a 120 V line, a resistance of how many ohms should be connected in series with the bulb
|
(a) 10 ohm |
(b) 20 ohm |
(c) 30 ohm |
(d) 40 ohm |
A wire of length L and 3 identical cells of negligible internal resistances are connected in series. Due to current, the temperature of the wire is raised by ∆ T in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross – section but of length 2 L. The temperature of the wire is raised by the same amount ∆ T in the same time t. the value of N is
|
(a) 4 |
(b) 6 |
(c) 8 |
(d) 9 |
Assertion : A laser beam 0.2 W power can drill holes through a metal sheet, whereas 1000 W torch-light cannot.
Reason : The frequency of laser light is much higher then that of torch light.
|
(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. |