In Bainbridge mass spectrograph a potential difference of 1000 V is applied between two plates distant 1 cm apart and magnetic field in B = 1T. The velocity of undeflected positive ions in m/s from the velocity selector is
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(a) |
(b) |
(c) |
(d) |
(c) 
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A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be
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(a) 1 mA |
(b) 2 mA |
(c) 4 mA |
(d) None of these |
Assertion : Coloured spectrum is seen when we look through a muslin cloth.
Reason : It is due to the diffraction of white light on passing through fine slits.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
If the distance between parallel plates of a capacitor is halved and dielectric constant is doubled then the capacitance
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(a) Decreases two times |
(b) Increases two times |
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(c) Increases four times |
(d) Remain the same |
Which of the following is true
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(a) Common base transistor is commonly used because current gain is maximum |
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(b) Common emitter is commonly used because current gain is maximum |
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(c) Common collector is commonly used because current gain is maximum |
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(d) Common emitter is the least used transistor |
