Question

A point charge `q_1 = -1.0 muC` is held stationary at the origin. A second point charge `q_2 = + 2.0 muC` moves from the point `(1.0 m, 0, 0)` to `(2.0 m, 0, 0)`. How much work is done by the electric force on `q_2`?

Answer 1

Work done by electrostatic forces
`-/_U`
`=U_i-U_f`
`=(1/(4piepsilon_0))(q_1q_2)(1/r_i-1/r_f)`
`=(9xx10^9)(-2xx10^-12)(1/1.0-1/2.0)`
`=-9xx10^-3J`
`=-9mJ`