Basics of RL Circuits

Quick Facts

  • Energy stored in an inductor will increase over time as current flows through a RL circuit.
  • Current will be equal to current of the battery as \(t\) approaches infinity.
  • Current will increase over time when switch is closed

Important tendencies to note

For the context of the next bullet points, imagine there is an RL circuit with a switch. Here are some important tendencies to note:

  • Suppose the switch is initially open. When the switch is closed, current will flow through the circuit. The inductor, though, will resist a change in current. What does this mean? Effectively, this means when the switch is initially closed (\(t=0\)), we can imagine no current goes through the inductor.
    • As \(t\) approaches \(\infty\), the inductor acts as a wire (no resistance).

Formula Reference

FORMULA: Time constant of RL Circuit

\[\tau = \frac{L}{R}\]

FORMULA: Current of RL Circuit

\[I = I_{0}(1 - e^{\frac{-t}{\tau}})\]