Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

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)

In the following arrangement of capacitors, the energy stored in the 6 µF capacitor is E. Find the value of the following :
(i) Energy stored in 12 µF capacitor.
(ii) Energy stored in 3 µF capacitor.
(iii) Total energy drawn from the battery.

 Draw a circuit diagram to determine internal resistance of a cell in the laboratory?

Find the charge on the capacitor as shown in the circuit.

Draw typical output characteristics of an n-p-n transistor in CE configuration. Show how these characteristics can be used to determine output resistance.

Find the ratio of energy stored in the two configurations if they are both connected to the same source.

The potential difference between the terminals of a 6.0 V battery is 7.2 V when it is being charged by a current of 2.0 A. What is the internal resistance of the battery?

The energy density in the electric field created by a point charge falls off with the distance from the point charge as

A capacitor of capacitance 500 μF is connected to a battery through a 10 kΩ resistor. The charge stored in the capacitor in the first 5 s is larger than the charge stored in the next.

(a) 5 s

(b) 50 s

(c) 500 s

(d) 500 s

A capacitor C₁ of capacitance 1 μF and a capacitor C₂ of capacitance 2 μF are separately charged by a common battery for a long time. The two capacitors are then separately discharged through equal resistors. Both the discharge circuits are connected at t = 0.

(a) The current in each of the two discharging circuits is zero at t = 0.

(b) The currents in  the two discharging circuits at t = 0 are equal but not zero.

(c) The currents in the two discharging circuits at t = 0 are unequal.

(d) C₁ loses 50% of its initial charge sooner than C₂ loses 50% of its initial charge.

Find the charge on the capacitor shown in the figure.