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Question
Justify your answers for each case.
State the significance of the negative value of electrostatic potential energy of a system of charges.
Three charges are placed at the corners of an equilateral triangle ABC of side 2.0 m as shown in the figure. Calculate the electric potential energy of the system of three charges.
Solution
U = `(KQ_AQ_B)/r + (KQ_BQ_C)/r + (KQ_CQ_A)/r`
U = `K/r[Q_AQ_B + Q_BQ_C + Q_CQ_A]`
U = `K/r xx [4 xx 10^-6 xx -4 xx 10^-6] + [-4 xx 10^-6 xx 2 xx 10^-6] + [2 xx 10^-6 xx 4 xx 10^-6]`
U = `K/r xx 10^-12[-16 - 8 + 8]`
U = `K/r xx 10^-12(-16)`
U = `(-9 xx 10^9 xx 10^-12 xx 16)/2`
U = -72 × 10-3 J
U = -7.2 × 10-2 J
A negative value signifies a stable system.
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