Question

Three point charges of +2q - 3q and -3q are placed at the vertices a b and c of an equilateral triangle of side 20cm what should be the magnitude and the nature of the charge q to be placed at the midpoint of m of bc so that the charge a remains in equilibrium

Answer 1

Answer:

Learning Objectives

By the end of this section, you will be able to:

Describe the electric force, both qualitatively and quantitatively

Calculate the force that charges exert on each other

Determine the direction of the electric force for different source charges

Correctly describe and apply the superposition principle for multiple source charges

Experiments with electric charges have shown that if two objects each have electric charge, then they exert an electric force on each other. The magnitude of the force is linearly proportional to the net charge on each object and inversely proportional to the square of the distance between them. (Interestingly, the force does not depend on the mass of the objects.) The direction of the force vector is along the imaginary line joining the two objects and is dictated by the signs of the charges involved.

Let

{q}_{1},{q}_{2}= the net electric charges of the two objects;

{\stackrel{\to }{\text{r}}}_{12}= the vector displacement from {q}_{1} to {q}_{2}.

The electric force \stackrel{\to }{\text{F}} on one of the charges is proportional to the magnitude of its own charge and the magnitude of the other charge, and is inversely proportional to the square of the distance between them:

F\propto \frac{{q}_{1}{q}_{2}}{{r}_{12}^{2}}.

This proportionality becomes an equality with the introduction of a proportionality constant. For reasons that will become clear in a later chapter, the proportionality constant that we use is actually a collection of constants. (We discuss this constant shortly.)

Coulomb’s Law