In an AC circuit that contains a resistor, a capacitor, and an inductor, impedance replaces the DC concept of resistance. Explain briefly the difference between the two quantities.

The function of resistance and impedance are the same that is to resist the flow of current so when they increase, the value of current decreases. But there are many differences also which are as follows

1) Impedance is relevant only in AC current because it is frequency dependent. When current is steady, its value becomes zero. In that case only resistance is functional. In a circuit having both capacitor and inductor, when frequency is small, its value is high. As frequency increases its value decreases. After reaching zero value, its value starts increasing again.

2) The resistance is dissipative in nature ie it converts some electric energy into heat energy. But impedence is not dissipative in nature. It does not waste electric energy ie it does not consume electric energy. That is why it is preferably used in ac circuits when current is to be reduced.