Which one of the following is heterosporous?

In the circuit shown,the current in the $1\,\Omega$ resistor is

What is the kinetic energy of an electron in the second excited state of $He^{+}$? (Energy of an electron in the first shell of $H = -13.6 \text{ eV}$)

Which of the following statements is not correct?

$A$ common emitter transistor amplifier has a current gain of $50$. If the load resistance is $4 \ k\Omega$ and input resistance is $500 \ \Omega$,the voltage gain of the amplifier is

Secondary sewage treatment is mainly a