Difference between Impedance and resistance

Impedance and resistance are both terms used in the context of electrical circuits, and while they both relate to the opposition to the flow of electric current, they have different meanings and behaviors.

Resistance

• Resistance (measured in ohms, symbol: Ω) is a property of a component or material that describes its opposition to the flow of direct current (DC). It's a measure of how much a material or component resists the flow of electrons.
• Resistors are components designed to introduce resistance into a circuit. The relationship between voltage (V), current (I), and resistance (R) is described by Ohm's Law: V = IR.
• In a purely resistive circuit, the phase difference between voltage and current is zero, meaning they are in phase. Resistance does not depend on the frequency of the AC signal.

Impedance

• Impedance is a more general term used in the context of alternating current (AC) circuits. It includes resistance but also accounts for the effects of reactance, which arises in components like capacitors and inductors when AC voltage is applied.
• Impedance is a complex quantity, meaning it has both a magnitude and a phase angle. It's represented as Z and can be broken down into resistance (R) and reactance (X), both of which are measured in ohms (Ω).
• Impedance depends on the frequency of the AC signal. As the frequency increases, inductor impedances increase while capacitor impedances decrease.