Nuclei — Physics STD 12 Science — Question

The energy stored in a 50 mH inductor carrying a current of 4 A will be

(a) 0.4 J

(b) 4.0 J

(c) 0.8 J

(d) 0.04 J

Figure shows a closed surface which intersects a conducting sphere. If a positive charged is placed at the point P, the flux of the electic field through the closed surface:

1. Will remain zero.
2. Will become positive.
3. Will become neagative.
4. Will become undefined.

In the given circuit, with steady current, the potential drop across the capacitor must be

(a) V

(b) V / 2

(c) V / 3

(d) 2V / 3

A plano convex lens (f = 20cm) is silvered at plane surface. Now f will be

(a) 20 cm

(b) 40 cm

(c) 30 cm

(d) 10 cm

The ratio of the frequencies of the long wavelength limits of Lyman and Balmer series of hydrogen spectrum is

(a) 27 : 5

(b) 5 : 27

(c) 4 : 1

(d) 1 : 4

Which of the following is not the property of a cathode ray

(a) It casts shadow	(b) It produces heating effect
(c) It produces flurosence	(d) It does not deflect in electric field

If the potential difference applied to the tube is doubled and the separation between the filament and the target is also doubled, the cutoff wavelength:

1. Will remain unchanged.
2. Will be doubled.
3. Will be halved.
4. Will become four times the original.

The amplification factor of a triode is 20 and trans-conductance is 3 milli mho and load resistance 3   then the voltage gain is

(a) 16.36

(b) 28

(c) 78

(d) 108

The maximum intensity of fringes in Young's experiment is I. If one of the slit is closed, then the intensity at that place becomes I_o. Which of the following relation is true ?

(a) I = Io	(b) I = 2Io
(c) I = 4Io	(d) There is no relation between I and Io

Mark the correct statement

(a) Nuclei of different elements can have the same number of neutrons

(b) Every element has only two stable isotopes

(c) Only one isotope of each element is stable

(d) All isotopes of every element are radioactive