- AInsulators
- BSemi-conductors
- CConductors
- DAlloys
Explanation:
Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, and semiconductors have their valence band filled, preventing the entry flow of new electrons.
Thus semi-conductors allows a large current to pass through them.
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Cathode rays are produced when the pressure is of the order of
|
(a) 2 cm of Hg |
(b) 0.1 cm of Hg |
(c) 0.01 mm of Hg |
(d) 1 μm of Hg |

Hubble's law states that the velocity with which the 'milky way' is moving away from the earth is proportional to
|
(a) Square of the distance of the milky way from the earth |
|
(b) Distance of milky way from the earth |
|
(c) Mass of the milky way |
|
(d) Product of the mass of the milky way and its distance from the earth |
The electric field between the plates of a parallel plate capacitor when connected to a certain battery I . If the space between the plates of the capacitor is filled by introducing a material of dielectric constant K without disturbing the battery connections, the field between the plates shall be
|
(a) |
(b) |
(c) |
(d) None of the above |
In AM, the centpercent modulation is achieved when
|
(a) Carrier amplitude = signal amplitude |
(b) Carrier amplitude ≠ signal amplitude |
|
(c) Carrier frequency = signal frequency |
(d) Carrier frequency ≠ signal frequency |
Two plane mirrors. A and B are aligned parallel to each other, as shown in the figure. A light ray is incident at an angle of 30° at a point just inside one end of A. The plane of incidence coincides with the plane of the figure. The maximum number of times the ray undergoes reflections (including the first one) before it emerges out is

|
(a) 28 |
(b) 30 |
(c) 32 |
(d) 34 |
The work function of aluminium is 4.2 eV. If two photons, each of energy 3.5 eV strike an electron of aluminium, then emission of electrons will be
|
(a) Possible |
|
(b) Not possible |
|
(c) Data is incomplete |
|
(d) Depend upon the density of the surface |