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 $\left.g=10 \,ms ^{-2}\right]$
$10$
$16$
$24$
$20$
Two identical conducting spheres carrying different charges attract each other with a force $F$ when placed in air medium at a distance $'d'$ apart. The spheres are brought into contact and then taken to their original positions. Now the two spheres repel each other with a force whose magnitude is equal to that of the the initial attractive force. The ratio between initial charges on the spheres is
Consider three charges $q_{1}, q_{2}, q_{3}$ each equal to $q$ at the vertices of an equilateral triangle of side $l .$ What is the force on a charge $Q$ (with the same sign as $q$ ) placed at the centroid of the triangle, as shown in Figure
Total charge $-\,Q$ is uniformly spread along length of a ring of radius $R$. A small test charge $+q$ of mass m is kept at the centre of the ring and is given a gentle push along the axis of the ring.
$(a) $ Show that the particle executes a simple harmonic oscillation.
$(b)$ Obtain its time period.
Two copper balls, each weighing $10\,g$ are kept in air $10\, cm$ apart. If one electron from every ${10^6}$ atoms is transferred from one ball to the other, the coulomb force between them is (atomic weight of copper is $63.5$)
Two electrons are separated by a distance of $1\,\mathop A\limits^o $. What is the coulomb force between them