Question

What is the amount of work done to bring a charge of 4*10^-3C charge from infinity to a point whose electric potential is 2*10^2V?

(a) 0.8J

(b) -0.8J

(c) 1.6J

(d) -0.4J

The question was posed to me during an interview for a job.

Enquiry is from Electrostatic Potential due to a Point Charge topic in portion Electrostatic Potential and Capacitance of Physics – Class 12

Answer 1

Correct answer is (a) 0.8J

The best I can explain: Work done = potential*charge by definition. We know that the potential of a point is the amount of work done to bring a unit charge from infinity to a certain point. Therefore, work done W=q*V=4*10^-3*200J=0.8J. The work done is positive in this case.