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education/physics/PHYS2220/Electric Charge.md

@@ -6,11 +6,14 @@
 	- The smallest discrete quantity of charge is $\frac{1}{3}e$.
 - In an isolated system, the net charge will always remain constant.
 
-# Electric Force
+# Coulomb's Law
 - Two charges will exert a force on each other along the line joining them.
 	- The magnitude of this force is proportional to the *product of the charges* and inversely proportional to the to the $\sqrt{dist}$.
 	- The equation to determine the force between two charges is as follows:
-	$$ \vec{F_{12} = \vec{r}k\frac{q_1q_2}{r^2}} $$
+	$$ \vec{F}_{12} = \vec{r}k\frac{q_1q_2}{r^2} $$
 		- $\vec{r}$ is a unit vector pointing from charge 1 to charge 2
-		- $k$ is Couloumb's constant, or $8.99 * 10^9 \frac{Nm^2}{C^2}$ 
-		- $q_1$ and $q_2$ 
+		- $k$ is Coulomb's constant, or $8.99 * 10^9 \frac{Nm^2}{C^2}$ 
+		- $q_1$ and $q_2$ are the charges
+		- $r$ is the distance between those charges
+		- The resulting force will push away if $q_1q_2$ is *positive*, and attract if $q_1q_2$ is negative. This is where the rule "opposites attract, like repels" comes from
+- Coulomb's law only holds exactly true for *point charges* i.e a proton