Key Equations

Average electrical current	$I_{ave} = \frac{Δ Q}{Δ t}$
Definition of an ampere	$1 A = 1 C/s$
Electrical current	$I = \frac{d Q}{d t}$
Drift velocity	$v_{d} = \frac{I}{n q A}$
Current density	$I = \iint_{area} \vec{J} \cdot d \vec{A}$
Resistivity	$ρ = \frac{E}{J}$
Common expression of Ohm’s law	$V = I R$
Resistivity as a function of temperature	$ρ = ρ_{0} [1 + α (T - T_{0})]$
Definition of resistance	$R \equiv \frac{V}{I}$
Resistance of a cylinder of material	$R = ρ \frac{L}{A}$
Temperature dependence of resistance	$R = R_{0} (1 + α Δ T)$
Electric power	$P = I V$
Power dissipated by a resistor	$P = I^{2} R = \frac{V^{2}}{R}$