An electron is taken from point A to point B along the path A B in a uniform electric field of intensity `E = 10 Vm^-1` side `AB = 5 m`, and side `BC = 3 m`. Then, the amount of work done on the electron by us is.
.

Options

A. 50 eV
B. 40 eV
C. `-50 eV`
D. `-40 eV`

Answer

b

Explanation

`W_(A B) = W _(A C) + W_(C B)`
`W_(C D)` should be zero, because in moving from `C to B`, we always move perpendicular to field. Hence, force applied by field and displacement will be at `90^(@)`.
`W_(A C) = - e(V_C - V_A)`
`V_C - V_A = - E xx A C = -10 xx 4 = -40`
`:. W_(A B) = e xx (-40) = 40 e`
So `W_(A B) = 40 e J = 40 e V`.