Magnetism And Matter — Physics STD 12 Science — Question

Which of the following planets have rings around it

(a) Uranus

(b) Mars

(c) Jupiter

(d) Saturn

The plate resistance of a triode is 2.5 × 10⁴ W and mutual conductance is 2 × 10^–3 mho. What will be the value of amplification factor

(a) 50

(b) 1.25 × 107

(c) 75

(d) 2.25 × 107

The electrical conductivity of pure germanium can be increased by:

If  millimho, then on increasing plate voltage by  50 V, how much the grid voltage is changed so that plate current remains the same

(a) – 2.86 V

(b) –  4 V

(c) + 4 V

(d) + 2 V

Two magnetic lines of force:

A solid sphere, a hollow sphere and a disc, all having same mass and radius, are placed at the top of an incline and released. The friction coefficients between the objects and the incline are same and not sufficient to allow pure rolling. Least time will be taken in reaching the bottom by:

1. The solid sphere.
2. The hollow sphere.
3. The disc.
4. All will take same time.

The work done against electrostatic force gets stored in which form of energy?

A radioactive element  decay into  . The number of β - particles emitted are

(a) 4

(b) 6

(c) 2

(d) 1

Assertion  :   Silicon is preferred over germanium for making semiconductor devices.

Reason      : The energy gap for germanium is more than the energy gap of silicon.

(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 ammeter A reads 2 A and the voltmeter V reads 20 V.  the value of resistance R is (Assuming finite resistance's of ammeter and voltmeter)

(a) Exactly 10 ohm	(b) Less than 10 ohm
(c) More than 10 ohm	(d) We cannot definitely say