Basics calculator
Reactance & resonance
A coil fights fast changes, a capacitor slow ones; at f0 they cancel.
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The example, worked out
Given
- Frequency
- 1 kHz
- Inductance L
- 10 mH
- Capacitance C
- 1 µF
Working
- grows with frequency
- shrinks with frequency
- where they are equal and cancel
Results
The formulas
- XL = 2π f Lgrows with frequency
- XC = 1 / (2π f C)shrinks with frequency
- f0 = 1 / (2π √(L C))where they are equal
The usual traps
- Below f0 a series LC looks capacitive, above it inductive.
- Real parts have losses: the resonance is only as sharp as their Q.
Questions
How do I calculate the reactance of an inductor or a capacitor?
XL = 2π f L: grows with frequency. XC = 1 / (2π f C): shrinks with frequency. f0 = 1 / (2π √(L C)): where they are equal.
What does it give for typical values?
XL 62.8 Ω, XC 159 Ω at 1 kHz; f0 = 1.59 kHz. XL at 1 kHz: 62.8 Ω; XC at 1 kHz: 159 Ω.
What are the usual mistakes?
Below f0 a series LC looks capacitive, above it inductive. Real parts have losses: the resonance is only as sharp as their Q.
In the app
Your circuit, drawn live
Change a value: the schematic redraws with your numbers on the parts.
The part you can buy
Results rounded to standard values (E12, E24, E96) and power ratings.
The working, shown
Every step written out. Try it first by hand, then check.
Into your notebook
One click puts the circuit on a sheet of your project.
Open the calculatorOpens in the app on 1 December, with Circuit Notebook 1.0
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