A positively charged pendulum is oscillating in a uniform electric field pointing upwards. Its time period as compared to that when it oscillates without electric field

Two charges $e$ and $3 e$ are placed at a distance $r$. The distance of the point where the electric field intensity will be zero is .........

Two point charges $q_{ A }=3\; \mu \,C$ and $q_{ B }=-3\; \mu \,C$ are located $20\; cm$ apart in vacuum.

$(a)$ What is the electric field at the midpoint $O$ of the line $AB$ joining the two charges?

$(b)$ If a negative test charge of magnitude $1.5 \times 10^{-9}\; C$ is placed at this point, what is the force experienced by the test charge?

A cube of side $'a'$ has point charges $+Q$ located at each of its vertices except at the origin where the charge is $- Q$. The electric field at the centre of cube is

For what type of charge distribution, electric field can be obtained by using Coulomb’s law and superposition principle ?

A hollow sphere of charge does not produce an electric field at any