Question

The electric potential at point A is 20 V and at B is -40 V. Find the work done by an external and electrostatic force in moving an electron slowly from B to A.

Answer 1

Answer:

w = vQ

Q = It

so , Q= 1.6 ×10^8

w = -60 × 1.6 × 10^8

Answer 2

The work done by an external and electrostatic force in moving an electron slowly from B to A is :

• Given : Electric potential at point A is 20 V and at B is -40 V, charge on electron = 1.6×10^-19 C

• For work done by external force,

Wex = q×( Vb - Va )

= q×(-40-20)

= -1.6×10^-19×60

= -96×10^-19 J

• For work done by electrostatic force,

Wes = q×( Va - Vb )

= q×( 20 + 40 )

= q×60

= 1.6×10^-19×60

= 96×10^-19J

• Hence, Wex = -Wes