ece106: add fields

docs/1b/ece106.md

@@ -180,13 +180,15 @@ $$\vec F_{12}=k\frac{Q_1Q_2}{||R_{12}||^2}\hat{R_{12}}$$
 
 An **electric dipole** is composed of two equal but opposite charges $Q$ separated by a distance $d$. The dipole moment is the product of the two, $Qd$.
 
-The charge experienced by a positive test charge along the dipole line can be reduced to:
+The charge experienced by a positive test charge along the dipole line can be reduced to as the ratio between the two charges decreases to the point that they are basically zero:
 $$\vec F_q=\hat x\frac{2kQdq}{||\vec x||^3}$$
 
-### Maxwell's theorems
+## Maxwell's theorems
 
 Compared to Coulomb's law, $Q_1$ creates an electric field around itself — each point in space is assigned a vector that depends on the distance away from the charge. $Q_2$ *interacts* with the field. According to Maxwell, as a charge moves, it emits a wave that carries information to other charges.
 
-The **electric field strength** $\vec E$ is the force per unit *positive* charge at a specific point:
+The **electric field strength** $\vec E$ is the force per unit *positive* charge at a specific point $p$:
 
-$$\vec E=\frac{\vec{F}}{q}$$
+$$\vec E_p=\lim_{q\to 0}\frac{\vec{F}}{q}$$
+
+Please see [SL Physics 1#Electric potential](/sph3u7/#electric-potential) for more information.