Magnetism And Matter — Physics STD 12 Science — Question

In the absence of other conductors, the surface charge density

(a) Is proportional to the charge on the conductor and its surface area

(b) Inversely proportional to the charge and directly proportional to the surface area

(c) Directly proportional to the charge and inversely proportional to the surface area

(d) Inversely proportional to the charge and the surface area

The dominant mechanisms for motion of charge carriers in forward and reverse biased silicon P-N junctions are

(a) Drift in forward bias, diffusion in reverse bias

(b) Diffusion in forward bias, drift in reverse bias

(c) Diffusion in both forward and reverse bias

(d) Drift in both forward and reverse bias

The slope of plate characteristic of a vacuum diode is  2   The plate resistance of diode will be

(a) 50 W

(b) 50 kW

(c) 500 kW

(d) 500 kW

The idea of matter waves was given by

(a) Davisson and Germer

(b) de-Broglie

(c) Einstein

(d) Planck

A circular loop carrying a current is replaced by an equivalent magnetic dipole. A point on the loop is in:

For watt-less power in an AC circuit the phase angle between the current and voltage is.

Carbon, silicon and germanium have four valence electrons each. At room temperature the appropriate statement is:

When a metal surface is illuminated by light of wavelengths 400 nm and 250 nm, the maximum velocities of the photoelectrons ejected are  v and 2v respectively. The work function of the metal is (h = Planck’s constant, c = velocity of light in air)

(a) 2hc

(b)

(c)

(d) 0.5

The focal length of lens of refractive index 1.5 in air is 30 cm.  When it is immersed in a liquid of refractive index , then its focal length in liquid will be

(a) 30 cm

(b) 60 cm

(c) 120 cm

(d) 240 cm