Resistors

A resistor opposes the flow of current like a restrictive pipe for fluid flow. As such, it determines how hard you need to push ($V$) to get charge to flow at a desired rate ($I$).

Ohm’s Law

$$V=IR$$

describes the relationship between voltage, current, and resistance

The inverse of resistance is conductance:

$$G=\frac{1}{R}\left[S=\frac{A}{V}\right]$$

Adding Resistors

Resistors in series add:

$$R_{eq}=R_1+R_2$$

Resistors in parallel add as inverses:

$$\frac{1}{R_{eq}}=\frac{1}{R_1}+\frac{1}{R_2}$$

This is equivalent to saying conductances in parallel add: $G_{eq}=G_1+G_2$