The Nucleus — Physics STD 12 Science — Question

Assertion  :  A transistor amplifier in common emitter configuration has a low input impedence.

Reason      : The base to emitter region is forward biased.

(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.

The power of a person's spectacle lenses is +2 D . He is suffering from which of the following defects?

X-ray from a Coolidge tube is incident on a thin aluminium foil. The intensity of the X-ray transmitted by the foil is found to be I₀. The heating current is increased to increase the temperature of the filament. The intensity of the X-ray transmitted by the foil will be:

A conducting disc of radius r spins about its axis with an angular velocity ω. There is a uniform magnetic field of magnetude B perpendicular to the plane of the disc. C is the centre of the ring.

The first line in the Lyman series has wavelength l. The wavelength of the first line in Balmer series is

(a)

(b)

(c)

(d)

A coil takes 15 min to boil a certain amount of water, another coil takes 20 min for the same process. Time taken to boil the same amount of water when both coil are connected in series

(a) 5 min

(b) 8.6 min

(c) 35 min

(d) 30 min

A lightning arrester must have the following property.

Who first proposed that light was wave-like in character?

A wire of resistance 10 W is bent to form a circle. P and Q are points on the circumference of the circle dividing it into a quadrant and are connected to a Battery of 3 V and internal resistance 1 W as shown in the figure.  The currents in the two parts of the circle are

(a)    and	(b)   and
(c)   and	(d)   and

Assertion   :   A metallic shield in form of a hollow shell may be built to block an electric field.

Reason       : In a hollow spherical shield, the electric field inside it is zero at every point.

(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.