Equation #12: Faraday’s Law of Electromagnetic Induction
Faraday was an excellent experimenter. He discovered the principle behind Generators and Electric Motors without knowing advanced mathematics! His law of electromagnetic induction states that if you change the magnetic flux going through a conducting coil/loop, an electromotive force, emf (or voltage) will develop in the coil which is equal to the rate of change of flux. The negative sign indicates that the emf will tend to oppose the change in magnetic flux through the coil. This tendency to oppose the change is known as Lenz law.
Magnetic flux can be visualized as the “amount of magnetic field lines” going through the conducting loop, and is equal to the integral of magnetic field B.dA, where A is area. The rate of change of this is the time derivative of the integral.
Actually, Maxwell modified Faraday’s law and the final form of Maxwell-Faraday equation states that a time-varying magnetic field will always accompany a spatially-varying, non-conservative electric field, and vice versa.
Faraday’s story has always inspired me to do my best and to learn new things. He was a self-learner who taught himself everything about electricity and magnetism, mostly by experiment.
To know more about him, see
Explanation of the law of Electromagnetic Induction
A simple experiment, just like what Faraday did
For more equations in the series, see Famous Equations in Physics.