Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions for Physics

Which of the following is not showing the essential difference between electrostatic shielding by a conducting shell and magnetostatic shielding?

Two parallel plate capacitors X and Y, have the same area of plates and same separation between plates. X has air and Y with dielectric of constant 2, between its plates. They are connected in series to a battery of 12 V. The ratio of electrostatic energy stored in X and Y is ______.

In the circuit shown in figure, initially K₁ is closed and K₂ is open. What are the charges on each capacitors.

Then K₁ was opened and K₂ was closed (order is important), What will be the charge on each capacitor now? [C = 1µF]

Two charges q₁ and q₂ are placed at (0, 0, d) and (0, 0, – d) respectively. Find locus of points where the potential a zero.

The capacitors, each of 4 µF are to be connected in such a way that the effective capacitance of the combination is 6 µF. This can be achieved by connecting ______.

A capacitor of capacity C₁ is charged to the potential of V₀. On disconnecting with the battery, it is connected with an uncharged capacitor of capacity C₂ as shown in the adjoining figure. Find the ratio of energies before and after the connection of switch S.

Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel. What is the total capacitance of the combination?

Write clearly, why in the case of a transistor (i) the base is thin and lightly doped

Write clearly, why in the case of a transistor (ii) the emitter is heavily doped.

Obtain the expression for the energy stored per unit volume in a charged parallel plate capacitor.

Differentiate between three segments of a transistor on the basis of their size and level of doping.

How is a transistor biased to be in active state?

Explain what would happen if the capacitor given in previous question a 3 mm thick mica sheet (of dielectric constant = 6) were inserted between the plates,

1. While the voltage supply remained connected.
2. After the supply was disconnected.

A 12 pF capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor?

A 600 pF capacitor is charged by a 200 V supply. It is then disconnected from the supply and is connected to another uncharged 600 pF capacitor. How much electrostatic energy is lost in the process?

A high tension (HT) supply of, say, 6 kV must have a very large internal resistance. Why?

Two towers on top of two hills are 40 km apart. The line joining them passes 50 m above a hill halfway between the towers. What is the longest wavelength of radio waves, which can be sent between the towers without appreciable diffraction effects?

Write the functions of the three segments of a transistor.

The figure shows the input waveforms A and B for ‘AND’ gate. Draw the output waveform and write the truth table for this logic gate.

Draw a typical input and output characteristics of an n-p-n transistor in CE configuration. Show how these characteristics can be used to determine (a) the input resistance (r₁), and (b) current amplification factor (β)