The electric potential at point A is 60 V and at B is - 90 V. Find the work done by an external force and electrostatic force, respectively, in moving an electron slowly from B to A.

Question

Question

This question was previously asked in

SSC JE Electrical 16 Nov 2022 Shift 3 Official Paper

Answer 1

The correct answer is option 3):(-240 × 10-19 J and 240 × 10-19 J)

Concept:

The work done by an external force to move a change from one point to another point is given

W = q ΔV

where

charge of electron

q = −1.6×10⁻¹⁹ C

ΔV is the change in potential

The electrostatic potential energy is

U = - W

Calculation:

q = −1.6×10 −19 C

Potential at A is 60 V

Potential at B is - 90 V

W = −1.6×10 −19( 60+ 90)

= - 240 ×10 −19 J

The electrostatic potential energy is

U = 240 ×10 −19 J