- AMetallic conductor.
- BGallium arsenide.
- CThyristor.
- Dp-n junction diode.
Explanation:
‘X’ is a metallic conductor. For small currents, it obeys Ohms’s law and its V-I graph is a straight line. But when large currents are passed through the same conductor, it gets heated up and its resistance increases. It no longer obeys Ohm’s law at higher currents.
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Through which character we can distinguish the light waves from sound waves
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(a) Interference |
(b) Refraction |
(c) Polarisation |
(d) Reflection |
A 60 watt bulb is hung over the center of a table 4 m × 4 m at a height of 3 m. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is
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(a) |
(b) 2 / 1 |
(c) 17 / 13 |
(d) 5 / 4 |
The current in a coil changes from 4 ampere to zero in 0.1 s. If the average e.m.f. induced is 100 volt, what is the self inductance of the coil
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(a) 2.5 H |
(b) 25 H |
(c) 400 H |
(d) 40 H |
Assertion : Free electron always keep on moving in a conductor even then no magnetic force act on them in magnetic field unless a current is passed through it.
Reason : The average velocity of free electron is zero.
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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. |
Assertion : Photoelectric effect demonstrates the wave nature of light.
Reason : The number of photoelectrons is proportional to the frequency of light.
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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. |
The ratio of intensities of two waves are given by 4 : 1. The ratio of the amplitudes of the two waves is
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(a) 2 : 1 |
(b) 1 : 2 |
(c) 4 : 1 |
(d) 1 : 4 |
Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell the work function of the cathode surface is 4.2 eV. In order to reduce the photo-current to zero the voltage of the anode relative to the cathode must be made
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(a) – 4.2 V |
(b) – 9.4 V |
(c) – 17.8 V |
(d) +9.4 V |
When the distance between the charged particles is halved, the force between them becomes
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(a) One-fourth |
(b) Half |
(c) Double |
(d) Four times |