Question

How much work must be done to bring three electrons from a great distance apart to within 9.0 × 10-10 m from one another (at the corners of an equilateral triangle)?

Answer 1

As we know that change in the potential energy of the system must be equal to the work done to bring the system of charges

here we know that

$U = 3\frac{kq_1q_2}{r^2}$

also here we have

$q_1 = q_2 = 1.6 \times 10^{-19} C$

$r = 9 \times 10^{-10} C$

now we will have

$U = \frac{9 \times 10^9 (1.6 \times 10^{-19})^2}{(9\times 10^{-10})^2}$

$U = 2.84 \times 10^{-10} J$

So here work done to bring three charges at the vertices of a triangle is given as

$W = 2.84 \times 10^{-10} J$