Question

A +2.00nC point charge is at the origin, and a second -5.00nC point charge is on the x-axis at x= 0.800m.

a) Find the magnitude of the net electric force that the two charges would exert on an electron placed at x = 0.200m on the x-axis.

b) Find the direction of the net electric force that the two charges would exert on an electron placed atx = 0.200m on the x-axis.

( ∘ counterclockwise from the +x-direction )

Answer 1

AB = 0.2 m

BC = AC - AB = 0.8 - 0.2 = 0.6 m

e = magnitude of charge on electron = 1.6 x 10^-19 C

F₁ = force on the electron by the charge Q₁ = k Q₁ e /AB² = (9 x 10⁹) (2 x 10^-9) (1.6 x 10^-19)/(0.2)² = 7.2 x 10^-17 N

F₂ = force on the electron by the charge Q₂ = k Q₂ e /AB² = (9 x 10⁹) (5 x 10^-9) (1.6 x 10^-19)/(0.6)² = 2 x 10^-17 N

Since both F₁ and F₂ are in same direction , hence net force on the electron is given as

F = F₁ + F₂ = (7.2 + 2) (10^-17) = 9.2 x 10^-17 N

b)

direction : towards left or towards negative X-axis