The number of revolutions per second made by an electron in the first Bohr orbit of hydrogen atom is ($h$ = Planck's constant, $m$ is the mass of electron and $r$ is the radius of the orbit.)

What does the following combination of gates produce?

In common emitter transistor amplifier, the output resistance is $500$ k$\Omega$ and the current gain $\beta = 50$. If power gain of amplifier is $5 \times 10^6$, what is the input resistance?

When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called