Two identically charged pith balls are suspended from the some point by two massless identical threads density of each ball is $\rho $. If system is immersed in a medium of density $\sigma $, balls remain undeflected, then the dielectric constant of medium is
$\frac{\rho }{{\rho - \sigma }}$
$\frac{ \rho - \sigma }{{\rho }}$
$\frac{\sigma }{{\rho - \sigma }}$
$\frac{ \rho - \sigma }{{\sigma }}$
In the given figure two tiny conducting balls of identical mass $m$ and identical charge $q$ hang from non-conducting threads of equal length $L$. Assume that $\theta$ is so small that $\tan \theta \approx \sin \theta $, then for equilibrium $x$ is equal to
An infinite number of charges, each of charge $1 \,\mu C$ are placed on the $x$-axis with co-ordinates $x = 1, 2,4, 8, ....\infty$. If a charge of $1\, C$ is kept at the origin, then what is the net force acting on $1\, C$ charge....$N$
When the distance between the charged particles is halved, the force between them becomes
Two small spheres each of mass $10 \,mg$ are suspended from a point by threads $0.5 \,m$ long. They are equally charged and repel each other to a distance of $0.20 \,m$. The charge on each of the sphere is $\frac{ a }{21} \times 10^{-8} \, C$. The value of $a$ will be ...... .
$\left[\right.$ Given $\left.g=10 \,ms ^{-2}\right]$
Two identical balls having like charges and placed at a certain distance apart repel each other with a certain force. They are brought in contact and then moved apart to a distance equal to half their initial separation. The force of repulsion between them increases $4.5$ times in comparison with the initial value. The ratio of the initial charges of the balls is