Electromagnetic Waves — Physics STD 12 Science — Question

If identical charges (-q) are placed at each corner of a cube of side b, then electric potential energy of charge (+q)  which is placed at centre of the cube will be

(a)

(b)

(c)

(d)

The angular spread of central maximum, in the diffraction pattern, does not depend on ______.

Two thin wire rings each having a radius R are placed at  a distance d apart with their axes coinciding. The charges on the two rings are +q  and -q. The potential difference between the centres of the two rings is

(a) Zero	(b)
(c)	(d)

Assertion  :   The electric bulbs glows immediately when switch is on.

Reason      : The drift velocity of electrons in a metallic wire is very high.

(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  main source of solar energy is

(a) Fission reactions	(b) Fusion reactions
(c) Chemical reactions	(d) Combustion reactions

Work function of lithium and copper are respectively 2.3 eV and 4.0 eV. Which one of the metal will be useful for the photoelectric cell working with visible light ? (h = 6.6 × 10^–34 J-s, c = 3 × 10⁸ m/s)

(a) Lithium

(b) Copper

(c) Both

(d) None of these

The new resistance of wire of R W, whose radius is reduced half, is

(a) 16 R

(b) 3 R

(c) 2R

(d) R

Force between the protons and neutrons in a nucleus is:

The effective resistance between the points  A and  B in the figure is

(a) 5Ω

(b) 2 Ω

(c) 3 Ω

(d) 4 Ω