Electromagnetic Oscillations and the Oscillating Circuit
How electric and magnetic energy trade places back and forth inside a coil and a capacitor
Big idea: If you connect a charged capacitor to a coil (inductor), the charge does not simply leak away. It swings back and forth: the capacitor discharges through the coil, the coil then recharges the capacitor the other way, and the cycle repeats. During this dance, energy keeps changing form between the electric field of the capacitor and the magnetic field of the coil. These repeating changes of charge, current and voltage are called electromagnetic oscillations, and the coil-plus-capacitor loop that produces them is the oscillating circuit.
By the end of this topic you will be able to:
- describe the parts of an oscillating (LC) circuit and what each one stores;
- explain how energy transforms between the electric and magnetic fields during one cycle;
- use Thomson's formula T = 2π√(LC) to find the period and frequency;
- tell the difference between damped and harmonic (undamped) oscillations;
- relate an LC circuit to a mechanical pendulum, and understand what an open circuit is.