Nuclei — Physics STD 12 Science — Question

Assertion  : Density of all the nuclei is same.

Reason      : Radius of nucleus is directly proportional to the cube root of mass number.

(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.

In an NPN transistor circuit, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, the emitter current (i_E) and base current (i_B) are given by

(a) iE = – 1 mA, iB = 9 mA	(b) iE = 9 mA, iB = – 1 mA
(c) iE = 1 mA, iB = 11 mA	(d) iE = 11 mA, iB = 1 mA

An electric bulb is rated 220 volt and 100 watt. Power consumed by it when operated on 110 volt is

(a) 50 watt

(b) 75 watt

(c) 90 watt

(d) 25 watt

One brass plate is inserted between two charges. The force between two charges will:

A positively charged ball hangs from a silk thread. We put a positive test charge  at a point and measure F/, then it can be predicted that the electric field strength E

(a)

(b)

(c)

(d) Cannot be estimated

The emf of a thermocouple, one junction of which is kept at 0℃, is given by  the Peltier co-efficient will be

(a) (t + 273) (a + 2bt)	(b) (t + 273) (a – 2bt)
(c) (t – 273) (a- 2bt)	(d) (t – 273) (a – 2bt)

Natural light from the sun is :

The potential difference applied to an X-ray tube is 5kV and the current through it is 3.2 mA. Then the number of electrons striking the target per second is

(a) 2

(b) 5

(c) 1

(d) 4

A long straight horizontal cable carries a current of 2.5 A in the direction 10° south of west to 10° north of east. The magnetic meridian of the place happens to be 10° west of the geographic meridian. The earth’s magnetic field at the location is 0.33 Gauss, and the angle of dip is zero. Locate the line of neutral points. (Ignore the thickness of the cable).

Minimum deviation is observed with a prism having angle of prism A, angle of deviation δ, angle of incidence i and angle of emergence e. We then have generally

(a) i > e

(b) i < e

(c) i = e

(d) i = e = δ