Question

A charge of 10 μC is brought from infinity to point P in an external electric field. Point P is located at a distance of 5 cm away from 5 μC charge. Calculate the work done to bring the 10 μC to point P from infinity?

• A. (A) 90 J
• B. (B) 9 J
• C. (C) 900 J
• D. (D) 9000 J

Answer 1

Answer: (B)

(B) 9 J

Answer 2

Explanation:
The electrostatic potential is given by:V=WqThe electrostatic potential due to a point charge is given by:V=Kqr[∵K=14πϵ0]Where W= Work, q= charge and r= distanceGiven: q1=5μC r=5 cm =5×10−2 m q2=10μCThe electric potential due to 5μC at a distance of 5 cm away from it isV=9×109×5×10−65×10−2=9×105VThe work done in moving the charge of 10μC from infinity to P is:W=V×q=9×105×10×10−6=9 JHence, the correct option is (B).