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In physics, induced electromotive force (EMF) is defined as the generation of potential difference due to a change in the magnetic flux of a coil. On the other hand, current is the rate at which electrons or ions flow in a closed circuit. Michael Faraday explained the relation between induced emf and current, which we will find out in the following sections.
What is Induced EMF?
EMF, or electromotive force, is known to be induced when the magnetic flux linking the conductor or coil changes.
ε = Electromagnetic Force, ∅ = Magnetic Flux, N = number of turns
There are two ways in which we can induce charge in a flux
Statically Induced EMF
In this, the EMF is induced while keeping both the coil and magnetic field stationary. This way, the change in flux takes place without moving the coil or the field system.
Dynamically Induced EMF
In this, either the magnetic field or conductor is kept moving while keeping the other stationary. For instance, when the magnetic field is kept moving, the conductor is stationary. By either of the two processes, the EMF is induced, and the conductor cuts across the magnetic field easily.
What is Current?
The flow of charge through a conducting body in a closed circuit is known as current. It is measured in Coulombs per second, and its SI unit is Ampere, denoted by A.
Effects of Electric Current
Heating Effect: When current flows through a conductor, heat is produced. This heating effect is represented by:
H = I2RT
Magnetic Effect: When current passes through a conductor, a magnetic field is built. This is similar to when we put a compass near a wire carrying a large amount of current and the needle of the compass starts to deflect.
Chemical Effect: When current is passed within a solution, a chemical reaction is said to occur, which breaks the solution down further into ions.
Differences between Induced EMF and Current
What is the Relation Between Induced EMF and Current?
Faraday discovered the relation between induced EMF and current while conducting several experiments. He took a cylindrical coil made up of insulated copper wire and connected it in series with a galvanometer. He then took a bar magnet, with the north pole pointing towards the coil, and moved it in an up-and-down motion. This led to the following observations, which showed the connection between induced EMF and current:
The galvanometer shows a deflection whenever there is a motion between the coil and magnet, thereby confirming the flow of induced current.
The deflection only happens when there is a motion between the coil and magnet.
The direction of the flow of current changes with a change in the position of the magnet.
The deflection depends on the speed of the magnet; the faster the magnet moves, the more is its deflection, and vice versa.
But when the south of the magnet is pointed towards the coil, there is a change in the direction of flow of current into the opposite direction. Although, the results are still the same.
He also demonstrated it through another experiment wherein he took two coils and placed both of them close to each other. He connected coil 1 to a battery and a rheostat with key ‘K’ and then connected coil 2 to a sensitive galvanometer and placed it near coil 1. On pressing the key ‘K’, the galvanometer showed momentary deflection. This indicates that current was being infused in coil 2 because of the current in coil 1 which increases with the magnetic flux linked to coil 1. This makes the magnetic flux linked to coil 2 increase as well. On releasing the key, the deflection is shown in the opposite direction, which indicates that the current was being induced again in coil 2 because the current in coil 1 decreases, hence decreasing the magnetic flux which further decreases in the same way in coil 2. This causes the deflection in the opposite direction of the galvanometer.
Faraday’s Laws
Faraday’s First Law: It states that the EMF is induced when the magnetic flux changes across the coil with time. There are a few ways in which one can change the intensity of the magnetic field in the loop: by moving the coil of the magnetic loop, by rotating the coil, by moving the magnet close or far from the coil, and changing the position of the coil in the magnetic field.
Faraday’s Second Law: The connection between induced EMF and current was the base of Faraday’s law which shows the relation between current and induced EMF. Faraday’s second law states that the induced EMF depends proportionally on the rate with which the flux changes.
ε = Electromagnetic Force, ∅ = Magnetic Flux, N = Number of turns
Conclusion
This article on the differences between induced EMF and current gave a perfect representation of the key features of both concepts. The relation between induced EMF and current was explained through Faraday’s experiments. Two of his experiments have been discussed in brief, explaining the relation between current and induced EMF and giving rise to a new term called electromagnetic induction, which involves both current and induced EMF.
