Explanation:
When we measure the emf of a cell by the potentiometer then no current flows in the circuit in zero-deflection condition ie, cell is in open circuit. Thus, in this condition the actual value of a cell is found. In this way, potentiometer is equivalent to an ideal voltmeter of infinite resistance.
Note. The emf in the potentiometer is measured by null method in which zero deflection position is found on the wire.
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Assertion : Basic difference between an electric line and magnetic line of force is that former is discontinuous and the latter is continuous or endless.
Reason : No electric lines of forces exist inside a charged body but magnetic lines do exist inside a magnet.
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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. |
In Millikan oil drop experiment, a charged drop of mass 1.8 
is stationary between its plates. The distance between its plates is 0.90 cm and potential difference is 2.0 kilo volts. The number of electrons on the drop is
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(a) 500 |
(b) 50 |
(c) 5 |
(d) 0 |
The characteristic X-ray radiation is emitted, when
| (a) The electrons are accelerated to a fixed energy |
| (b) The source of electrons emits a monoenergetic beam |
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(c) The bombarding electrons knock out electrons from the inner shell of the target atoms and one of the outer electrons falls into this vacancy |
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(d) The valence electrons in the target atoms are removed as a result of the collision |
An ideal transformer has 500 and 5000 turn in primary and secondary windings respectively. If the primary voltage is connected to a 6V battery then the secondary voltage is
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(a) 0 |
(b) 60 V |
(c) 0.6 V |
(d) 6.0 V |
Light of two different frequencies whose photons have energies 1eV and 2.5eV respectively, successively illuminates a metal of work function 0.5eV. The ratio of maximum kinetic energy of the emitted electron will be
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(a) 1 : 5 |
(b) 1 : 4 |
(c) 1 : 2 |
(d) 1 : 1 |
A silver and a copper voltmeters are connected in parallel across a 6 volt battery of negligible resistance. In half an hour, 1 gm of copper and 2 gm of silver are deposited. The rate at which energy is supplied by the battery will approximately be (Given E.C.E. of copper = 3.294 
and E.C.E. of silver = 1.118 
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(a) 64 W |
(b) 32 W |
(c) 96 W |
(d) 16 W |
In an interference arrangement similar to Young's double slit experiment, the slits S1 and S2 are illuminated with coherent microwave sources each of frequency 106 Hz. The sources are synchronized to have zero phase difference. The slits are separated by distance d = 150 m. The intensity I (𝜃) is measured as a function of q, where q is defined as shown. If I0 is maximum intensity, then I(θ) for 0 ≤ θ ≤ 90° is given by
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(a) I(θ) = |
(b) I(θ) = |
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(c) I(θ) = |
(d) a, b |
