Alternating Current — Physics STD 12 Science — Question

Two charges are placed a certain distance apart in air. If a brass plate is introduced between them, the force between them will:

The number of electrons to be put on a spherical conductor of radius 0.1m to produce an electric field of 0.036 N/C  just above its surface is

(a) 2.7

(b) 2.6

(c) 2.5

(d) 2.4

What is the potential energy of the equal positive point charges of 1μC each held 1 m apart in air

(a) 9

(b) 9

(c) 2 eV/m

(d) Zero

The two bulbs as in the above question are connected in series to a 200 volt line. Then

(a) The potential drop across the two bulbs is the same

(b) The potential drop across the 40 watt bulb is greater than the potential drop across the 100 watt bulb

(c) The potential drop across the 100 W bulb is greater than the potential drop across the 40 W bulb

(d) The potential drop across both the bulb is 200 volt

Light of wavelength 4000 Å is incident on a sodium surface for which the threshold wave length of photo – electrons is 5420 Å. The work function of sodium is

(a) 4.58 eV

(b) 2.29 eV

(c) 1.14 eV

(d) 0.57 eV

If the energy of a photon corresponding to a wavelength of 6000 Å is 3.32 , the photon energy for a wavelength of 4000 Å will be

(a) 1.4 eV

(b) 4.9 eV

(c) 3.1 eV

(d) 1.6 eV

Doppler's effect is sound in addition of relative velocity between source and observer, also depends while source and observer or both are moving. Doppler's effect in light depend only on the relative velocity of source and observer. The reason of this is.

A generator has an e.m.f. of 440 volt and internal resistance of 400 ohm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is:

The most penetrating radiation out of the following is

(a) X-rays

(b) β -rays

(c) α -  particles

(d) γ - rays

The equivalent resistance of the following infinite network of resistances is

(a) Less than 4 Ω	(b) 4 Ω
(c) More than 4 Ω  but less than 12 Ω	(d) 12 Ω