Superposition
$$ \vec{F}_{net} = \vec{F}_1 + \vec{F}_2 + \cdots $$
Selected source
2 total
Source charge q
i
+3
units
Test charge Q
+2
units
Positive charge
Negative charge
Forces on Q
Net force
Add +
Add -
Remove
Reset
Net = 0
Vertical cancels
Line distribution
Near dominates