Glossary:Impedance

For most practical purposes, impedance is the same as resistance, and also measured in ohms. Resistance is the number of steady volts you need to push a steady amp through a circuit, but if the voltage is AC or is varying, then inductance and capacitance add a kind of momentum and springiness to the way the current responds to the voltage. The volts per amp is then likely to be different, and is termed impedance.