A charge $Q$ is placed at each of the opposite corners of a square. A charge $q$ is placed at each of the other two corners. If the net electrical force on $Q$ is zero, then $\frac{Q}{q}=$ ______
$-2 \sqrt 2$
$-1$
$1$
$-$$\frac{1}{{\sqrt 2 }}$
Write limitations of Coulomb’s law.
Two particle of equal mass $m$ and charge $q$ are placed at a distance of $16\, cm$. They do not experience any force. The value of $\frac{q}{m}$ is
Two similar spheres having $ + \,q$ and $ - \,q$ charge are kept at a certain distance. $F$ force acts between the two. If in the middle of two spheres, another similar sphere having $ + \,q$ charge is kept, then it experience a force in magnitude and direction as
Two identical tennis balls each having mass $m$ and charge $q$ are suspended from a fixed point by threads of length $l$. What is the equilibrium separation when each thread makes a small angle $\theta$ with the vertical?
Two identical metallic spheres $A$ and $B$ when placed at certain distance in air repel each other with a force of $F$. Another identical uncharged sphere $C$ is first placed in contact with $A$ and then in contact with $B$ and finally placed at midpoint between spheres $A$ and $B$. The force experienced by sphere $C$ will be.