A simple pendulum oscillates with an angular amplitude $\theta$. If the maximum tension in the string is 4 times the minimum tension then the value of $\theta$ is

An electron moves in Bohr orbit. The magnetic field at the centre is proportional to

The r.m.s. speed of gas molecules at 800 K will be

If the charge on the capacitor is increased by 3C, the energy stored in it increases by $21 \%$. The original charge on the capacitor is