Electric Charges and Fields — Physics STD 12 Science — Question

Intensity of an electric field E due to a dipole, depends on distance r as

(a) E ∝

(b) E ∝

(c) E ∝

(d) E ∝

The transition of electron from n = 4, 5, 6, ………. to n = 3 corresponds to:

An inductor of 2 henry and a resistance of 10 ohms are connected in series with a battery of 5 volts. The initial rate of change of current is

(a) 0.5 amp/sec

(b) 2.0 amp/sec

(c) 2.5 amp/sec

(d) 0.25 amp/sec

Conventional flow of current will always be from:

A coil of self inductance 50 henry is joined to the terminals of a battery of e.m.f. 2 volts through a resistance of 10 ohm and a steady current is flowing through the circuit. If the battery is now disconnected, the time in which the current will decay to 1/e of its steady value is

(a) 500 seconds

(b) 50 seconds

(c) 5 seconds

(d) 0.5 seconds

Four charges are placed on corners of a square as shown in figure having side of 5cm. If Q is one microcoulomb, then electric field intensity at centre will be

(a) 1.02  upwards	(b) 2.04  downwards
(c) 2.04  upwards	(d) 1.02  downwards

Intensity of X-rays depends upon the number of

(a) Electrons

(b) Protons

(c) Neutrons

(d) Positrons

The minimum energy required to remove an electron is called:

In Young’s double slit experiment the wavelength of light was changed from 7000 Å to 3500 Å. While doubling the separation between the slits which of the following is not true for this experiment

(a) The width of the fringes changes

(b) The colour of bright fringes changes

(c) The separation between successive bright fringes changes

(d) The separation between successive dark fringes remains unchanged

In a PN-junction diode not connected to any circuit

(a) The potential is the same everywhere

(b) The P-type is a higher potential than the N-type side

(c) There is an electric field at the junction directed from the N- type side to the P- type side

(d) There is an electric field at the junction directed from the P-type side to the N-type side