RLC Circuits
Consider what happens when resistors, capacitors, and inductors are combined in one
circuit. If all three components are present, the circuit is known as an RLC circuit (or
LRC). If only two components are present, it's either an RC circuit, an RL circuit, or
an LC circuit.
The overall resistance to the flow of current in an RLC circuit is known as the
impedance, symbolized by Z. The impedance is found by combining the resistance,
the capacitive reactance, and the inductive reactance. Unlike a simple series circuit
with resistors, however, where the resistances are directly added, in an RLC circuit the
resistance and reactances are added as vectors.
This is because of the phase relationships. In a circuit with just a resistor, voltage and
current are in phase. With only a capacitor, current is 90° ahead of the voltage, and
with just an inductor the reverse is true, the voltage leads the current by 90°. When all
three components are combined into one circuit, there has to be some compromise.
To figure out the overall effective resistance, as well as to determine the phase
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 Fall '10
 DavidJudd
 Physics, Inductor, Electrical resistance, LC circuit, RLC Circuits

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