Question

You are given two metal spheres on portable insulating stands, a glass rod, and a piece of silk. Explain how to give the spheres exactly equal magnitudes of the same sign of charge.

Answer 1

Figure (a) shows two uncharged metallic sphere on an insulating metal stand.

Now, by rubbing the piece of silk and glass rod the rod will aquire a negative charge.

Bring this negatively charged rod close to the metallic sphere, as shown in Fig. (b). As the rod is brought close to the sphere, the free electrons in the sphere move away due to repulsion and start piling up at the farther end. The near end becomes positively charged due to deficit of electrons. This process of charge distribution stops when the net force on the free electrons inside the
metal is zero. Connect the sphere to the ground by a conducting wire. The electrons will flow to the ground while the positive charges at the near end will remain held there due to the attractive force of the negative charges on the rod, as shown in Fig(c). Disconnect the sphere from the ground. The positive charge continues to be held at the near end [Fig.(d)]. Remove the electrified rod. The positive charge will spread uniformly over the sphere as shown in Fig (e).

Now brought this positively charge sphere near the uncharged shere and touch each other as shown in Fig.(f)

Due to conduction charge will flow from charge spheres to uncharged shere. As the both spheres are identical so the charge will distribute equally among each other and finally after the equilibrium reach saparate the both spheres as shown in Fig. (g)

In this way we can charge the two metallic sphere equally and of same sign.