Electrostatic Potential Energy
Two charges q1 and q2 are placed 30 cm apart, as shown in the figure. A third charge q3 is moved along the arc of a circle of radius 40 cm from C to D.
The change in the potential energy of the system is where k is

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Answer: (c)
- stays cm from (it moves on a circle centred at A), so only the term changes.
- At C: cm. At D: cm.
- So , answer (c).