Energia armazenada indutor

Energy stored in an inductor

When current runs through an inductor, it stores energy in its magnetic field. The energy works out to E = ½ · L · I², where L is inductance in henries (H) and I is current in amperes, giving a result in joules (J). For an example, a 100 mH coil carrying 5 A stores E = 0.5 · 0.1 · 25 = 1.25 J. Capacitors keep their energy in an electric field; inductors do the opposite job and fight changes in current. When the current drops, the field collapses and gives that energy back. That is precisely how switched-mode power supplies (SMPS) swing between storing and releasing energy at high frequency to step voltage up or down.

Applications

You'll find them in buck/boost converters, the SMPS topologies that bank energy each switching cycle. Electric motors rely on them too, since the rotor windings hold rotational energy in their fields. Ignition coils in cars and Tesla coils take a low current to charge the inductor, then let a sudden collapse throw off kilovolts. And maglev trains use superconducting coils to store large amounts of energy for levitation and propulsion.

FAQ

Why does current squared matter so much? Because doubling the current quadruples the stored energy. In a large inductor, that means even a small current spike can park a dangerous amount of energy.

What happens if I open the circuit suddenly? The inductor insists on keeping the current going, so it throws off a high voltage spike (back-EMF) that can wreck switches. That is the reason flyback diodes sit across relay coils.

Does an ideal inductor lose energy? No. An ideal inductor stores and hands back energy with no loss. Real ones carry winding resistance and core losses that bleed off part of the energy as heat.