If 3 charges are placed at the vertices of equilateral triangle of charge ' \(q\) ' each. What is the net potential energy, if the side of equilateral triangle is \(\ell \mathrm{cm}\). (A) $\left[1 /\left(4 \pi \epsilon_{0}\right)\right]\left(3 q^{2} / \ell\right)$ (B) $\left[1 /\left(4 \pi \epsilon_{0}\right)\right]\left(2 q^{2} / \ell\right)$ (C) \(\left[1 /\left(4 \pi \epsilon_{0}\right)\right]\left(q^{2} / \ell\right)\) (D) $\left[1 /\left(4 \pi \epsilon_{0}\right)\right]\left(4 q^{2} / \ell\right)$

Short Answer

Expert verified
The net potential energy of three charges placed at the vertices of an equilateral triangle with side length \(\ell\) and charge \(q\) each is given by \(\frac{3 q^{2}}{(4\pi\epsilon_0\ell)}\), and the correct answer is option (A) \(\left[1/\(4 \pi \epsilon_{0}\)\right]\left(3 q^{2}/\ell\right)\).

Step by step solution

01

Understand the system of charges

There are 3 charges of magnitude 'q' placed at the vertices of an equilateral triangle. This means there are three pairs of charges whose interactions contribute to the total potential energy. Remember the formula for the potential energy between two charges: \(U = \frac{(k*q1*q2)}{r}\).
02

Calculate the potential energy between each pair of charges

The potential energy for each pair of charges is the same since all charges have the same magnitude and the distances between them are equal (since it's an equilateral triangle). The potential energy between any two charges is \(U = \frac{(k*q*q)}{\ell}\), where the constant \(k = 1/\(4 \pi \epsilon_{0}\) is Coulomb's constant.
03

Sum up the potential energy from all pairs

Since there are three pairs of charges, simply multiply the result from the previous step by 3. Therefore, the total potential energy is \(3*U = 3*\frac{(k*q*q)}{\ell} = \frac{(3 * k* q^{2})}{\ell}\).
04

Replace and solve

Substituting the value of \(k = 1/\(4 \pi \epsilon_{0}\), the total energy becomes \(\frac{3 q^{2}}{(4\pi\epsilon_0\ell)}\). Therefore, the correct answer is option (A) \(\left[1/\(4 \pi \epsilon_{0}\)\right]\left(3 q^{2}/\ell\right)\).

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