Be able to calculate the electric field (E = kq/r²) surrounding a charge: (remember it's affected the space around it, somewhat analogous to the gravitational field)

Be able to calculate the Voltage (V = kq/r)

Be able to calculate the force between two charges (F = kq₁q₂/r² and remember, F = qE which relates the force to the electric field)

where k = 8.99 x 10⁹ Nm²/C² q = the charge, r = the distance from the charge

Example

Find the electric field at 0.2 meters:

E = kq/r²

E = (8.99 x 10⁹ Nm²/C²)(2.3 x 10^-6)/(0.2 m)²

E = ______ N/C

The Voltage is given by

V = kq/r

using the same #'s

and if a 2.5 x 10^-6 C charge is placed 0.5 m away, then the force between them is given by:

F = kq₁q₂/r²

F = (8.99 x 10⁹ Nm²/C²)(2.3 x 10^-6)(2.5 x 10^-6)/(0.5 m)²

F = ________ N

recall also that the force is given by F = qE so if you know the electric field at that location, you can easily calculate the force on the charge, q.