Energy in Capacitor & Inductor

Stored Energy

Capacitors and inductors don't dissipate energy like resistors — they store it.

Capacitor

A capacitor stores energy in the electric field between its plates:

E_C = ½ · C · V²

Units: farads × volts² = joules

Inductor

An inductor stores energy in its magnetic field:

E_L = ½ · L · I²

Units: henries × amperes² = joules

Total Energy in RLC Circuit

The total stored energy at any instant:

E_total = ½·C·V_C² + ½·L·I²

In an underdamped RLC circuit, energy oscillates between the capacitor and inductor, gradually dissipated by R.

Practical Examples

Note: energy scales as V² for capacitors — doubling the voltage stores 4× the energy.

Applications

• Camera flash: large capacitor discharged quickly through a xenon tube
• Power supply filtering: capacitor releases stored energy during current spikes
• Inductive kickback: inductor's stored energy causes voltage spike when current is interrupted

Your Task

Implement double stored_energy(double c, double vc, double l, double il) that returns the total stored energy E = ½·C·V_C² + ½·L·I_L².