Bring a negatively charged rod close to a metallic sphere placed on a insulated stand. 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 stops when the net force on the free electrons inside the metal is zero.

Connect the sphere to the ground while the positive charges at the near end will remain held there due to the attractive forces of the negative charges on the rod. Disconnect the sphere from the ground. The positive charge continues to be held at the near end. Remove the electrified rod. The positive charge will spread uniformly over the sphere.

Is the above statements true? If true why is it true? I want a proof like "The potential of the sphere is greater than zero, hence there will be a flow of charge."

If false what is the correct statement?


1 Answer 1


The earth is at a much larger electrostatic-potential, than the sphere is. So, positive charges flow from the earth to the sphere, the number (I speak of number because charge is quantized) of which is equal to the number of electrons that accumulate in the farther end of the sphere. So, due to balance of charges at the farther end, the sphere loses its negative charge on the farther-end, and the positive charges get distributed uniformly all over the sphere. This explanation is based on the conventional flow of current.

Actual scenario is that, not positive charges, but rather the free-electrons in the metal of which the sphere is composed, are the real charge-carriers. These electrons, because of the existing electrostatic potential-gradient, existing between the earth and the sphere, flow through the conducting-wire, from the sphere, to the earth. Then the positive-charges are distributed uniformly, all over the sphere.

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