Inductor Calculator
Reactance, energy and the L/R time constant.
Work out Inductor. Reactance, energy and the L/R time constant. Names the misconception directly.
Total inductance
2 mH
Series — inductances add · reactance 12.566 Ω at 1,000 Hz
Inductors combine the same way as resistors — series adds, parallel divides — which makes them the easy half of this. The useful figure is the reactance: 2πfL, which rises in proportion to frequency. That rise is why an inductor passes DC almost freely and chokes high frequencies, and it is the whole basis of filters, chokes and transformers. Double the frequency and you double the opposition. The L/R time constant sets how quickly current builds when voltage is applied. After one time constant the current has reached 63% of its final value, and it is essentially there after five — the same shape as an RC circuit, with the roles of voltage and current swapped.
How the Inductor Calculator works
Total inductance in series or parallel, with reactance at a chosen frequency, the energy stored in the magnetic field, and the L/R time constant. Reactance rises in proportion to frequency, which is the whole reason inductors exist.
Also known as: inductive reactance at frequency · combine inductors · energy stored in an inductor · l over r time constant
Frequently asked questions
How do inductors combine?
The same way as resistors: series adds, parallel takes the reciprocal sum. That assumes no magnetic coupling between them — coupled inductors behave differently and become a transformer.
What is inductive reactance?
The opposition an inductor presents to alternating current, equal to 2πfL. It rises in proportion to frequency, so an inductor passes DC almost freely and blocks high frequencies.
How much energy does an inductor store?
Half L I squared, in the magnetic field. That stored energy is why breaking an inductive circuit produces a voltage spike — the field collapses and the energy has to go somewhere.
What is the L/R time constant?
How quickly current builds when voltage is applied. After one time constant the current reaches 63% of its final value and it is essentially there after five — the same shape as an RC circuit with voltage and current swapped.
Why do inductive loads need flyback diodes?
Because interrupting the current forces the collapsing magnetic field to dump its energy, and with nowhere to go it appears as a large reverse voltage spike that destroys switching transistors. A diode gives the current a path.
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