Electrical Engineering/Quick Reference

Basics

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  • Voltage: (V or v - Volts) The electrical potential between two points in a circuit.
  • Current: (I or i - Amperes) The amount of charge flowing through a part of a circuit.
  • Power: (W - Watts) Simply P = IV. It is the current times the voltage.
  • Source: A voltage or current source is the supplier for the circuit.
  • Resistor: (R measured in Ω - Ohms) A circuit element that "constricts" current flow.

Ohms law   or equivalently   or  

Resistors in series  

Voltage Divider  

Resistors in Parallel  

and for the special case of two resistors in parallel:  

Kirchhoff’s Voltage law: The algebraic sum of the voltages around a closed circuit path must be zero.

Kirchhoff’s Current Law: The sum of the currents entering a particular point must be zero.

Capacitors

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Capacitors in an AC circuit:  

In parallel:  

In series  

Inductors

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Inductors in an AC circuit:  

In parallel:  

In series:  

Special case: Two straight parallel wires