In what form is energy stored in an electric coil?

When electric current passes through a coil (also called an inductor), it does not store energy as heat or as an electric field — it stores energy in the form of a magnetic field that builds up around and through the coil. Every time current flows, the coil creates a magnetic field, and this magnetic field is where all the energy gets locked up until it is needed again.

• Inductor principle: a coil carrying current generates a magnetic field around it — the stronger the current, the stronger the magnetic field and the more energy stored
• Energy formula: energy stored in a coil is given by E = ½LI², where L is inductance and I is the current flowing through it
• Electromagnetic induction: when current changes, the magnetic field changes too — this changing field induces a voltage that opposes the change, as per Lenz's law
• Practical use: this magnetic energy storage principle is used in transformers, electric motors, inductors, and power supply circuits worldwide
• Capacitor vs coil: a capacitor stores energy in an electric field, while a coil stores energy in a magnetic field — this distinction is frequently tested in competitive exams