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Self-inductance
Intermediate
Coil opposes changing current.
ε = −L dI/dtA coil resists changes in its own current: ε = −L dI/dt, where L = NΦ/I in henrys. It acts like inertia for current.
L = 0.5 H, current changing 10 A/s: 5 V.
Switching off an inductive load can cause a spark.
In more detail
Self-inductance L relates the flux through a circuit to its own current, Φ = LI. A changing current induces an emf in the same circuit, ε = −L dI/dt, opposing the change.
Real-world uses
- Inductors in circuits limit rapid changes in current.
- Ignition coils use self-inductance to produce high voltages.
- Electrical engineers use inductors to smooth current in power supplies and to tune radio circuits.
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Frequently asked questions
What are the units?
Henries.
What does self-inductance do?
It makes current change gradually, acting like inertia for current.
What is inductance?
The property of a coil that opposes changes in the current through it, measured in henries.
Related topics in Magnetism & Induction
Motional emf · Eddy currents · Eddy current braking · Inductance of a solenoid · Energy in an inductor · Mutual inductance