Find the Point Where Electric Field is Zero: A Charge Problem

[Ruleski]

Homework Statement

A pair of charges sits on the x-axis, a charge Q1 = +9 nC at the origin and Q2 = +4 nC at x = 5. Assume no other charges are present. All coordinates are in meters.

At which one of these points is the net electric field equal to zero?

Homework Equations

The Attempt at a Solution

 

[Ruleski]

Follow up questions:

What is the potential at x = -5 ?

How much work is required to move the +4 nC charge (Q2) from its original location at x = 5 to x = 3 ?

Any explanation would help?
Thank You

 

[graphene]

The field can be zero at a point only if the fields due to the two charges cancel out at that point.
In which region can this happen? Left of Q1 / between Q1 and Q2 / right of Q2 ?
In each region you could draw the field vectors due to each charge & see where they could possibly cancel out.

Moving on to the follow up questions, do you know the potential due to a charge? And, how work is related to potential ?