# The Differences Between Resistance, Reactance, and Impedance

AC circuits are often complex to analyze since voltage and current alternate direction with a given frequency. These circuits have resistance and another property known as reactance. Impedance is the combination of resistance and reactance.

Resistors prevent current from flowing, meaning they have the property of resistance. Resistors are found in both AC and DC circuits and the energy that they prevent from flowing is expelled as heat. Mathematically, resistance is calculated as voltage divided by current.

Reactance is a property that opposes a change in current and is found in inductors and capacitors. It is specific to AC power and depends on the frequency of the current because it only affects such changing current. When reactance is present, it creates a 90 degree phase shift between voltage and current. The direction of the shift depends on whether the component is an inductor or a capacitor. These are known as inductive reactance or capacitive reactance.

Impedance is the combination of resistance and reactance and is a more complex number because it contains both real (resistance) and imaginary (reactance) parts.

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