Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and has high melting point ?

A common emitter amplifier has a voltage gain of 50, an input impedance of 100 $$\Omega $$ and an output impedance of 200 $$\Omega $$. The power gain of the amplifier is

The symbolic representation of four logic gates are given below



The logic symbols for OR, NOT and NAND gates are respectively

A transistor is operated in common-emitter configuration at V_C = 2V such that a change in the base current from 100 $$\mu $$A to 200 $$\mu $$A produces a change in the collector current from 5 mA to 10 mA. The current gain is