Resistors

Resistance, in terms of physical dimensions:

$$R = \frac{\rho l}{A}$$

Here:

• $l$: length
• $A$: cross-sectional area
• $\rho$: resistivity

If a voltage $V$ is applied across a conductor, then a given current $I$ will flow through the conductor $V \propto I$. The proportionality constant is called resistance $R$.

$$R = \frac{V}{I}$$