Electrostatic Potential and Capacitance - Result Question 16

18. As per the diagram, a point charge +q is placed at the origin O. Work done in taking another point charge Q from the point A [coordinates (0,a)] to another point B [coordinates (a,0)] along the straight path AB is:

[2005]

(a) zero

(b) (qQ4πε01a2)2a

(c) (qQ4πε01a2)a2

(d) (qQ4πε01a2)2a

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Answer:

Correct Answer: 18. (a)

Solution:

  1. (a) We know that potential energy of two charge system is given by

U=14πϵ0q1q2r According to question,

UA=14πϵ0(+q)(Q)a=14πε0Qqa

and UB=14πϵ0(+q)(Q)a=14πε0Qqa

ΔU=UBUA=0

We know that for conservative force, W=ΔU=0



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