Nuclei — Physics STD 12 Science — Question

A radioactive sample with a half life of 1 month has the label : “Activity=2 micro curies on 1.8.1991.'' What will be its activity two months later

(a) 1.0 micro curies

(b) 0.5 micro curies

(c) 4 micro curies

(d) 8 micro curies

To get an output Y=1 from the circuit above, the input must be:

Assertion   :   Neutral temperature of a thermocouple does not depend upon temperature of cold junction.

Reason    : Its value is constant for the given metals of the couple.

(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 SI unit of electric flux is:

A parallel plate capacitor has a plate separation of 0.01 mm and use a dielectric (whose dielectric strength is 19 KV/mm) as an insulator. The maximum potential difference that can be applied to the terminals of the capacitor is

(a) 190 V

(b) 290 V

(c) 95 V

(d) 350 V

A solid is completely immersed in a liquid. The force exerted by the liquid on the solid will.

1. Increase if it is pushed deeper inside the liquid.
2. Change if its orientation is changed.
3. Decrease if it is taken partially out bf the liquid.
4. Be in the vertically upward direction.

Two copper balls, each weighing 10g are kept in air 10 cm apart. If one electron from every  atoms is transferred from one ball to the other, the coulomb force between them is (atomic weight of copper is 63.5)

(a) 2.0

(b) 2.0

(c) 2.0

(d) 2.0

A point object is placed at a distance of 30 cm from a convex mirror of focal length 30cm. The image will form at

(a) Infinity	(b) Focus
(c) Pole	(d) 15 cm behind the mirror

In a typical Wheatstone network, the resistances in cyclic order are A = 10 W, B = 5 W, C = 4 W and D = 4 W for the bridge to be balanced

(a) 10 W should be connected in parallel with A

(b) 10 W should be connected in series with A

(c) 5 W should be connected in series with B

(d) 5 W should be connected in parallel with B

A hollow metal sphere of radius 5cm is charged such that the potential on its surface is 10V. The potential at a distance of 2cm from the centre of the sphere

(a) Zero

(b) 10 V

(c) 4 V

(d) 10/3 V