Electrostatics

Electric Charge

• Charge of an Electron: $-e$, where $e$ is the elementary charge

Coulomb's Law

• Force between two point charges: $F = k\frac{q_1q_2}{r^2}$, where $k$ is the Boltzmann's Constant

Electric Field

• Vector field surrounding an electric charge that exerts force on other charges
• Electric field strength $E = \frac{F}{q} = k \frac{Qq}{r^2} \cdot{1}{q} = k \frac{Q}{r^2}$
• $F$ and $E$ experienced by $q$ in electric field due to $Q$
• SI unit of $E$: $\mathrm{NC^{-1}}$

Electric Potential

• Work done moving a unit positive charge from a reference point to a specific point: $V = \frac{W}{q}$
• Typical reference point: Earth or a point at infinity 
• Work done moving $q$ across $\triangle V$ is $W = q \triangle V$
• Electric potential due to a charge $Q$ at distance $r$ from the charge is $V = \frac{1}{4 \pi \epsilon_{0}} \cdot \frac{Q}{r}$
• Electrical potential energy of a charge $q$ at a point with potential $V$ is $U = q V$
• Electric field $E$ between two parallel plates with distance $d$ apart and with potential difference $V$ is uniform: $E = \frac{V}{d}$