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How to Calculate the Equivalent Impedance in an AC Circuit

As electrons flow through a metallic wire, they scatter off one another and off wire boundaries. For direct current, or DC, electricity this phenomena is known as resistance and it is a key macroscopic quantity. Alternating current, or AC, electricity has a voltage that oscillates up and down with time. The electrical impedance of a component is a measure of the opposition to AC current flow. The equivalent impedance is a measure of the impedance in a complete AC circuit, consisting of a number of elements. You can calculate it using a set of simple rules.

Instructions

- 1
  Draw a diagram of the electrical circuit. Label each of the impedance values for each resistor in the circuit.
- 2
  Find all sets of resistors that are in series. Resistors are in series when current has to flow through one to get to the next. You can calculate the equivalent impedance of a set of resistors in series from the following equation:
  
  Zc = Z1 + Z2 + Z3, etc.
  
  Where Zc is the equivalent impedance and Z1, Z2 and Z3 are the impedance values of the individual resistors.
- 3
  Find all sets of resistors that are in parallel. Resistors are in parallel when they share two terminals. You can calculate the equivalent impedance of a set of resistors in parallel from the following equation:
  
  1/ Zc= 1/Z1 + 1/Z2 + 1/Z3, etc.
  
  Where Zc is the equivalent impedance and Z1, Z2 and Z3 are the impedance values of the individual resistors.

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