Inductance is the property of an electrical conductor that opposes changes in current flow by inducing an electromagnetic field.

Inductance

Inductance is a fundamental property in electromagnetic theory that describes how a conductor resists changes in electrical current by storing energy in a magnetic field. This phenomenon was first systematically studied by Michael Faraday during his groundbreaking work on electromagnetic induction.

Physical Principle

When electric current flows through a conductor, it generates a magnetic field. Any change in this current causes a corresponding change in the magnetic field, which in turn induces a voltage that opposes the original change in current. This self-reinforcing property is called inductance.

Key Components

Self-inductance: The property of a single conductor interacting with its own magnetic field
Mutual inductance: The interaction between two or more conductors through their magnetic fields
Electromagnetic induction: The broader principle governing these interactions

Measurement and Units

Inductance is measured in henries (H), named after Joseph Henry. One henry represents the inductance that produces a voltage of one volt when the current changes at a rate of one ampere per second.

Common magnitudes include:

Microhenries (μH): typical for small inductors
Millihenries (mH): common in power supplies
Henries (H): found in large power systems

Applications

Inductance plays a crucial role in many electronic devices and systems:

Power supplies: Filtering and energy storage
Radio frequency circuits: Tuning and filtering
Electric motors: Converting electrical to mechanical energy
Transformers: Voltage conversion and isolation

Practical Considerations

Engineers must carefully consider inductance in circuit design:

Parasitic inductance: Unwanted inductance in circuit traces
Magnetic coupling: Interference between components
Resonant circuits: Interaction with capacitance
Electromagnetic interference: Shielding and protection

Mathematical Description

The basic equation relating inductance (L), voltage (v), and current (i):

v = L(di/dt)

Where:

v is the induced voltage
L is the inductance in henries
di/dt is the rate of change of current with respect to time

Impact on Circuit Behavior

Inductance significantly affects circuit dynamics through:

Phase shift between voltage and current
Energy storage in magnetic fields
Impedance at different frequencies
Transient response characteristics

Understanding inductance is essential for designing and analyzing: