Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

As the temperature of a conductor increases, its resistivity and conductivity change. The ratio of resistivity to conductivity:

1. Increases.
2. Decreases.
3. Remains constant.
4. May increase or decrease, depending on the actual temperature.

The force between the plates of a parallel plate capacitor of capacitance C and distance of separation of the plates d  with a potential difference V between the plates, is

(a)

(b)

(c)

(d)

If the potential at each point on a conductor is same to each other, then:

A charge q  is placed at the centre of the open end of cylindrical vessel. The flux of the electric field through the surface of the vessel is

(a) Zero

(b)

(c)

(d)

The photo-electrons emitted from a surface of sodium metal are such that        

(a) They all are of the same frequency

(b) They have the same kinetic energy

(c) They have the same de Broglie wavelength

(d) They have their speeds varying from zero to a certain maximum

Semiconductor is damaged by the strong current due to

(a) Lack of free electron	(b) Excess of electrons
(c) Excess of proton	(d) None of these

There is some liquid in a closed bottle. The amount of liquid remains constant as time passes. The vapour in the remaining part:

1. Must be saturated.
2. Must be unsaturated.
3. May be unsaturated.
4. There will be no vapour.

In the given figure, when key k is closed, then direction of induced current in the coil B IS:

Assertion  :  Thin films such as soap bubble or a thin layer of  oil on water show beautiful colours when illuminated by white light.

 Reason     : It happens due to the interference of light reflected from the upper surface of the thin film.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

A rod of a certain metal is 1.0 m long and 0.6 cm in diameter.  Its resistance is 3.0 ×   ohm.  Another disc made of the same metal is 2.0 cm in diameter and 1.0 mm thick.  What is the resistance between the round faces of the disc

(a) 1.35 ×   ohm

(b) 2.70 ×   ohm

(c) 4.05 ×   ohm

(d) 8.10 ×   ohm