What is Faraday's law?

Faraday's law states that the induced EMF in a coil equals the negative rate of change of magnetic flux through the coil: EMF = −N × ΔΦ/Δt, where N is the number of turns, ΔΦ is the change in flux in webers, and Δt is the time interval in seconds.

What does the negative sign mean?

The negative sign reflects Lenz's law — the induced EMF drives a current that opposes the change in flux. This calculator shows both the signed EMF (with direction) and its magnitude.

What unit is magnetic flux?

Magnetic flux is measured in webers (Wb). One weber equals one volt-second (V·s). For a uniform field, flux = B × A × cos(θ), where B is field strength in teslas and A is the area in square meters.

Can the initial flux be greater than the final flux?

Yes. If ΔΦ is negative (flux decreasing), EMF is positive by the formula. The sign simply indicates the polarity of the induced voltage relative to the chosen reference direction.

What if the time interval is zero?

A zero time interval is physically undefined (instantaneous infinite EMF). The calculator will flag this as invalid. Use a very small but nonzero Δt to approximate rapid changes.

Faraday Induced EMF Calculator

Name: Faraday Induced EMF Calculator
Availability: InStock
Author: Nham Vu

Calculate the induced electromotive force in a coil from the rate of change of magnetic flux using Faraday's law.

Inputs

EMF = −N × ΔΦ / Δt

Number of Turns (N)

Must be a positive integer.

Initial Magnetic Flux Φ₁ (Wb)

Final Magnetic Flux Φ₂ (Wb)

Time Interval Δt (s)

Result

Enter values and click Calculate EMF.

Formula Breakdown

Calculated values will appear here.

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Summary

Calculate the induced electromotive force in a coil from the rate of change of magnetic flux using Faraday's law.

How it works

Enter the number of turns in the coil (N).
Enter the initial and final magnetic flux values (in webers).
Enter the time interval over which the flux changes.
The calculator applies EMF = −N × (ΔΦ / Δt) to find the induced voltage.
The magnitude and sign of the EMF are both displayed.

Use cases

Solve physics homework problems involving electromagnetic induction.
Design transformer and generator coils for engineering projects.
Verify analytical solutions for Faraday's law problems.
Explore how coil turns and flux rate affect induced voltage.
Teach or learn the relationship between flux change and EMF.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu