The principle of LASER action involves

• amplification of particular frequency emitted by the system

• population inversion

• stimulated emission

• All of the above

Give the truth table and circuit symbol for NAND gate.

A p–n junction (D) shown in the figure can act as a rectifier. An alternating current source (V) is connected in the circuit.

The logic circuit shown below has the input waveforms ‘A’ and ‘B’ as shown. Pick out the correct output waveform.


output is

A working transistor with its three legs marked P, Q and R are tested using a multimeter. No conduction is found between P and Q. By connecting the common (negative) terminal of the multimeter to R and the other (positive) terminal of P or Q, some resistance is seen on the multimeter. Which of the following is true for the transistor?

In the circuit below, A and B represent two inputs and C represents the output. The circuit represents

If in a p-n junction diode, a square input signal of 10V is applied as shown Then the output signal across RL will be 

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?

A thermocouple is made from two metals, Antimony and Bismuth. If one junction of the couple is kept hot and the other is kept cold then, an electric current will