Q19. An electron rotates in a circle around a nucleus having positive charge Ze. Correct relation between total energy (E) of electron to its potential energy (U) is :\\
(1) $\mathrm { E } = \mathrm { U }$\\
(2) $2 \mathrm { E } = \mathrm { U }$\\
(3) $2 \mathrm { E } = 3 \mathrm { U }$\\
(4) $\mathrm { E } = 2 \mathrm { U }$