Understanding Inductance
Inductance is the property of a conductor by which a change in current induces a voltage (electromotive force) opposing the change. It's measured in henries (H). Faraday's law gives induced voltage: V = -L(dI/dt), where L is inductance and dI/dt is current change rate. The negative sign (Lenz's law) indicates opposition to change. Inductors (coils) create magnetic fields when current flows. For a solenoid, L = ????n^2Al, where n is turns per length, A is area, l is length, and ?? is relative permeability.
Energy Storage in Magnetic Fields
Inductors store energy in magnetic fields: E = ?LI^2. Energy increases with inductance and current squared. Unlike capacitors (which store energy in electric fields), inductors resist changes in current. When current is interrupted, inductors generate high voltages trying to maintain current flow-this is why disconnecting inductive loads (motors, transformers) can create sparks. Inductors and capacitors together create LC circuits with resonant frequencies, fundamental to radio tuning, filters, and oscillators.
Applications in Electronics
Inductors are essential in power electronics and RF circuits. They smooth current in power supplies (while capacitors smooth voltage). Transformers use mutual inductance to transfer power between circuits at different voltages. Chokes block AC while passing DC. LC filters separate signals by frequency. Electric motors and generators operate on electromagnetic induction principles. Induction cooktops use high-frequency AC in coils to induce currents (and heat) in cookware. Understanding inductance is crucial for power supply design, motor control, wireless charging, and RF engineering.
Quick Tips
- Always verify units are consistent
- Use scientific notation for very large/small numbers
- Results are approximations — real conditions may vary
Frequently Asked Questions
A henry (H) is the SI unit of inductance. One henry means that a current change of 1 ampere per second induces 1 volt. Practical inductors range from microhenries (?H) to hundreds of henries (large transformers).
When current changes, the inductor's magnetic field changes, inducing a voltage (by Faraday's law) that opposes the change (Lenz's law). This makes current increase or decrease gradually, not instantly.
Inductors store energy in magnetic fields and oppose current changes (pass DC, block AC at high frequencies). Capacitors store energy in electric fields and oppose voltage changes (block DC, pass AC at high frequencies). They have complementary properties.
When current is interrupted, dI/dt becomes very large, inducing a very high voltage (V = -L dI/dt) as the inductor tries to maintain current flow. This high voltage can ionize air, creating a spark.
LC circuits contain inductors and capacitors. Energy oscillates between magnetic field (inductor) and electric field (capacitor) at resonant frequency f = 1/(2pisqrtLC). They're used in radio tuning, filters, and oscillators.