Back EMF Calculator
Compute the back electromotive force of an inductor (ε = −L·di/dt).
Input Data
Inductance H
H
Current Change A
A
Time Change S
s
Results
ε = −L·ΔI/Δt.
0V
Inductance H
0H
ΔI/Δt.
200A/s
At a glance:ε = −L·di/dt, opposing the change in current. Complements faraday-law and inductive-reactance.
Formula
ε = −L·(di/dt).
$$\varepsilon = -L\frac{dI}{dt}, \quad |\varepsilon| = L\left|\frac{\Delta I}{\Delta t}\right|, \quad U = \frac{1}{2}LI^2$$How to Use
- Enter L, current change and time.
- The tool returns the back EMF.
Case Studies
L=0.1 H, ΔI=2 A, Δt=0.01 s
ε = 20 V.
FAQ
Why a minus sign?
Lenz's law: it opposes the change in current.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.