Three-point charges q, – 4q and 2q are placed at the vertices of an equilateral triangle ABC of side '*l*' as shown in the figure. Obtain the expression for the magnitude of the resultant electric force acting on the charge q

(b) Find out the amount of the work done to separate the charges at infinite distance.

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#### Solution

\[F_{net} = \frac{2K q^2}{l^2}\cos {30}^0 + \frac{4K q^2}{l^2}\cos {30}^0 \]

\[ = \frac{3\sqrt{3}K q^2}{l^2}\]

\[ = \frac{3\sqrt{3}K q^2}{l^2}\]

(b) PE_{initial }=

\[- \frac{8K q^2}{l} - \frac{4K q^2}{l} + \frac{2K q^2}{l}\]

\[ = - \frac{10K q^2}{l}\]

PE_{final }= 0

Workdone = PE_{final }- PE_{initial }=

\[\frac{10K q^2}{l}\]

Concept: Coulomb’s Law

Is there an error in this question or solution?

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