Lei de Faraday
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
ε = −dΦ/dt
About this calculator
The Faraday's Law calculator determines the electromotive force (ε) induced in a circuit due to the change in magnetic flux (Φ) over time. The formula used is ε = −dΦ/dt, where the negative sign represents Lenz's Law, indicating that the induced current opposes the flux change. This tool is useful for students and professionals in electrical engineering and physics.
To use the calculator, enter the initial and final magnetic flux values (in webers) and the time interval (in seconds). The result is the average induced electromotive force in volts. The calculator assumes a linear change in flux over time, which is a valid approximation for many educational problems and simple practical applications.
Faraday's Law is fundamental in electromagnetism, forming the basis for electric generators, transformers, and inductors. It is applied in designing motors, power transmission systems, and induction devices. Understanding this law helps predict circuit behavior in varying magnetic fields.
Cautions: The formula ε = −dΦ/dt is valid for closed circuits. In situations with complex geometries or nonlinear variations, integration or simulations may be required. Also, the unit of magnetic flux is the weber (Wb) and time in seconds (s). Ensure values are in correct units to avoid errors.
Frequently asked questions
What is magnetic flux?
Magnetic flux (Φ) is the measure of the amount of magnetic field passing through a surface. It is calculated as the product of the magnetic field and the area perpendicular to it, in webers.
Why does the formula have a negative sign?
The negative sign represents Lenz's Law, which states that the induced electromotive force generates a current that opposes the change in magnetic flux that produced it.
Does this calculator work for any type of flux variation?
It calculates the average electromotive force for a linear change in flux over time. For nonlinear variations, differential calculus or more advanced simulations would be needed.
What units should I use?
Use magnetic flux in webers (Wb) and time in seconds (s). The result will be in volts (V).
Can I use it to calculate voltage in a transformer?
Yes, Faraday's Law is the basis for transformer operation. The induced voltage in each winding depends on the change in common magnetic flux.