Science (English Medium) Class 12 - CBSE Question Bank Solutions

The gain factor of an amplifier in increased from 10 to 12 as the load resistance is changed from 4 kΩ to 8 kΩ. Calculate (a) the amplification factor and (b) the plate resistance.

Use Einstein’s photoelectric equation to show how from this graph, 
(i) Threshold frequency, and (ii) Planck’s constant can be determined.

How does one explain the emission of electrons from a photosensitive surface with the help of Einstein’s photoelectric equation? 

Answer the following question.
Why photodiodes are required to operate in reverse bias? Explain.

Answer the following question.
Define the term "Intensity" in the photon picture of electromagnetic radiation.

Answer the following question.
Two infinitely long straight wire A₁ and A₂ carrying currents I and 2I flowing in the same direction are kept' distance apart. Where should a third straight wire A₃ carrying current 1.5 I be placed between A₁ and A₂ so that it experiences no net force due to A₁ and A₂? Does the net force acting on A₃ depend on the current flowing through it?

Use Einstein's photoelectric equation to show how from this graph,
(i) Threshold frequency, and
(ii) Planck's constant can be determined.

A variable resistor R is connected across a cell of emf ε and internal resistance r as shown in the figure. Draw a plot showing the variation of
(i) Terminal voltage V and
(ii) the current I, as a function of R.

Choose the correct answer from given options
Photons of frequency v are incident on the surface of two metals A and B of threshold frequency 3/4 v and 2/3 v, respectively. The ratio of maximum kinetic energy of electrons emitted from A to that from B is

If 10⁹ electrons move out of a body to another body every second, how much time is approximately required to get a total charge of 1C on the other body?

Electrostatic force is the force exerted by ______.

If a charge q₀ is there in an electric field caused by several point charges q_i. The potential energy of q₀ is given by ________.

If a current I is flowing in a straight wire parallel to x-axis and magnetic field is there in the y-axis then, ______.

According to Ampere's circuital law, ______.

Magnetic intensity is given by ______.

If `vec"H"` = magnetic intensity, `chi` = susceptibility, magnetic moment per unit volume `vec"M"` equals ______.

According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal versus the frequency of the incident radiation gives a straight line, whose slope ______.

Each photon has the same speed but different ______.

Basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc are ______.

Diffusion in a p-n junction is due to ______.