Science (English Medium) इयत्ता १२ - CBSE Important Questions for Physics

In a potentiometer arrangement for determining the emf of a cell, the balance point of the cell in open circuit is 350 cm. When a resistance of 9 Ω is used in the external circuit of the cell, the balance point shifts to 300 cm. Determine the internal resistance of the cell.

Using the concept of free electrons in a conductor, derive the expression for the conductivity of a wire in terms of number density and relaxation time. Hence obtain the relation between current density and the applied electric field E.

Write the underlying principle of a moving coil galvanometer.

State Ampere’s circuital law.

Define mutual inductance.

What do you understand by the statement, "Electromagnetic waves transport momentum"?

A point charge q is at a distance of d/2 directly above the centre of a square of side d, as shown the figure. Use Gauss' law to obtain the expression for the electric flux through the square.

Draw a necessary arrangement for winding of primary and secondary coils in a step-up transformer. State its underlying principle and derive the relation between the primary and secondary voltages in terms of number of primary and secondary turns. Mention the two basic assumptions used in obtaining the above relation.

Why does an unpolarised light incident on a polaroid get linearly polarised ?

Draw graphs showing variation of photoelectric current with applied voltage for two incident radiations of equal frequency and different intensities. Mark the graph for the radiation of higher intensity.

Draw the necessary energy band diagrams to distinguish between conductors, semiconductors and insulators.
How does the change in temperature affect the behaviour of these materials ? Explain briefly.

Draw a circuit diagram of a transistor amplifier in CE configuration.

Write S.I unit of electric flux.

Define Electric Flux.

A resistance of R Ω draws current from a potentiometer as shown in the figure. The potentiometer has a total resistance R_o Ω. A voltage V is supplied to the potentiometer. Derive an expression for the voltage across R when the sliding contact is in the middle of the potentiometer.

Derive an expression for the mutual inductance of two long co-axial solenoids of same length wound one over the other,

State the underlying principle of a cyclotron. Write briefly how this machine is used to accelerate charged particles to high energies

Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer?

Identify the part of the electromagnetic spectrum which is suitable for radar system used in aircraft navigation.

Write two uses of the following radiation.

X-rays