The Faraday Law is one of the cornerstones of electromagnetic field theory, explaining the principle that time-varying magnetic fields generate electric fields. This law mathematically defines the relationship between electricity and magnetism, and determines how a magnetic field affecting an electric circuit can induce an electrical effect.
Michael Faraday
Basic Principle of Faraday's Law
Faraday's Law states that a time-varying magnetic field induces an electric field along a closed loop dependent on the magnetic field. This law explains the interaction of electric fields with magnetic fields and enables the conversion of electrical energy into magnetic energy. The general formulation of Faraday's Law is as follows:
Here:
- The electric field around a closed loop (circulation),
- ΦB: Magnetic flux [Wb],
- dΦB/dt: Rate of change of magnetic flux.
The term on the right-hand side of the equation represents the rate of change of magnetic flux over time, which creates an electric field. According to Faraday’s Law, the electric field generated by the time-varying magnetic flux always attempts to oppose the change in the magnetic flux. This characteristic aligns with the principle of energy conservation and forms the basis of electromagnetic induction.
Induced Electromotive Force (emf)
Faraday's Law states that a change in the magnetic field induces an electric force (electromotive force or emf). This force usually arises around a wire loop or coil and can drive an electric current. The electromotive force (emf) is measured in volts and represents the work done per unit charge.
When there is a change in the magnetic field around a wire loop, an electric current is induced in the wire. This current can convert electrical energy into mechanical energy. According to Faraday's Law, the magnitude of this electromotive force depends on the rate of change of the magnetic field and the characteristics of the wire loop. One of the most significant outcomes of Faraday's Law is that changing magnetic fields can generate electrical energy without the need for an external energy source.
According to Faraday’s Law, the electromotive force (emf) in a circuit is proportional to the rate of change of the magnetic flux. This relationship can be calculated as:
Where N represents the number of turns of the coil, and ΔΦB refers to the change in magnetic flux [Wb]. As the magnetic flux changes in a coil, an emf is generated around the coil. The magnitude of this emf depends on the number of coil turns and the rate of change in magnetic flux. Therefore, increasing the number of turns in the coil will increase the induced emf.
Direction of the Induced Field
The negative sign in Faraday's Law indicates the direction of the induced (dynamic) field. According to Lenz's Law, the electromotive force induced to produce a current will try to oppose the change in the magnetic flux. In other words, a current is generated that works to counteract the change in the magnetic field. For example, when a magnet is rapidly brought near a wire loop, a current is induced in the wire. This current opposes the increase in the magnetic field and attempts to weaken it.
As the speed of the magnet increases, the magnetic flux through the wire loop also increases. In this case, a current is generated in the wire loop. According to Lenz's Law, this current tries to oppose the motion of the magnet by generating a magnetic field that counteracts the magnet’s movement. This results in the magnet’s motion being slowed down by the wire loop.
Applications of Faraday's Law
Faraday's Law forms the foundation for many technological applications in daily life. Devices like electric generators, transformers, and electric motors are based on the principles of Faraday’s Law. Electric generators use the movement of a magnetic field to produce electrical energy. Transformers, on the other hand, alter the voltage levels of electrical energy by changing the magnetic field of alternating current.
In electric motors, electrical current moves in a magnetic field to produce mechanical energy. Faraday's Law explains the relationship between the change in the magnetic field and the electric current, making it a crucial principle in engineering and physics.
Faraday's Law explains the principle that magnetic fields generate electric fields and lay the foundation for electromagnetic induction. As part of Maxwell’s equations, it helps in understanding the interactions between electricity and magnetism. Lenz's Law determines the direction of these interactions and ensures the conservation of energy. Both Faraday’s Law and Lenz’s Law form the basis of modern electrical devices and electromagnetic technologies, playing a significant role in the development of technologies such as electric generators, motors, and transformers commonly used in everyday life.
