In an electron gun the control grid is given a negative potential relative to cathode in order to
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(a) Decelerate electrons |
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(b) Repel electrons and thus to control the number of electrons passing through it |
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(c) To select electrons of same velocity and to converge them along the axis |
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(d) To decrease the kinetic energy of electrons |
(b) Repel electrons and thus to control the number of electrons passing through it
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The negative Zn pole of a Daniel cell, sending a constant current through a circuit, decreases in mass by 0.13g in 30 minutes. If the electrochemical equivalent of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is
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(a) 0.242 g |
(b) 0.190 g |
(c) 0.141 g |
(d) 0.126 g |
A 4μF conductor is charged to 400 volts and then its plates are joined through a resistance of 1kΩ. The heat produced in the resistance is
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(a) 0.16 J |
(b) 1.28 J |
(c) 0.64 J |
(d) 0.32 J |
In the figure, current through the 3 Ω resistor is 0.8 ampere, then potential drop through 4 Ω resistor is
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(a) 9.6 V |
(b) 2.6 V |
(c) 4.8 V |
(d) 1.2 V |
Assertion : Conductors having equal positive charge and volume, must also have same potential.
Reason : Potential depends only on charge and volume of conductor.
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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. |
When a bar magnet falls through a long hollow metal cylinder fixed with its axis vertical, the final acceleration of the magnet is
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(a) Equal to zero |
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(b) Less than g |
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(c) Equal to g |
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(d) Equal to g in to beginning and then more than g |
The energy of a hydrogen atom in its ground state is -13.6eV. The energy of the level corresponding to the quantum number n = 2 (first excited state) in the hydrogen atom is
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(a) – 2.72 eV |
(b) – 0.85 eV |
(c) – 0.54 eV |
(d) – 3.4 eV |
A voltmeter essentially consists of
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(a) A high resistance, in series with a galvanometer |
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(b) A low resistance, in series with a galvanometer |
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(c) A high resistance in parallel with a galvanometer |
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(d) A low resistance in parallel with a galvanometer |