Definition: Statically induced EMF is the voltage generated in a stationary coil when a changing magnetic flux links with it, either by self-induction or mutual induction.
What is Statically Induced EMF?
In the Statically induced EMF, as its name suggests, the field coils and the conductor or coil remain static. There is no physical movement of the magnetic field coil and the conductor. In this condition, it is possible to induce EMF in the coil by producing the varying magnetic field in the field coils.
Explanation of Statically Induced EMF
When the field coils receive the alternating current, it produces a varying magnetic field. Though, both the coils- magnetic field coils & conductor or coil is stationary, the varying magnetic flux produce EMF in the stationary coil.
This concept is based on Faraday’s Law of Electromagnetic Induction, which states that a time-varying flux linking a conductor induces EMF in it.
Types of Statically Induced EMF
We can further classify the statically induced EMF into two categories. They are;
- Self-induced Induced EMF
- Mutually Induced EMF
Self-induced Induced EMF
The induced EMF in the coil caused by the change of the coil’s own magnetic flux that links with it is called self-induced EMF.
Explanation of Self-Induced EMF
On pressing the key(K), the current flows in the coil, and the current changes its state from zero to finite value. This change in the current changes the magnetic flux linking to the coil. The changing magnetic flux linking to the coil produces self-induced EMF according to Faraday’s law of electromagnetic induction. The direction of the induced EMF is in such a way that it opposes the flow of current.
Self-Induced EMF Formula
The mathematical expression for self-induced EMF is;
Where:
- e =Self- induced EMF
- L = Self-inductance of coil
- dI/dt = Rate of change of flux
Mutually Induced EMF
When we place two coils near to each other, and the current flow in one coil, then the changing magnetic flux in the current-carrying coil induces EMF in the neighboring coil. This induced EMF is called mutually induced EMF.
Explanation of Mutually Induced EMF
We consider two coils, coil-1 and coil-2 placed near each other. When the circuit of coil-1 completes, the current flow through the coil-1 and produces magnetic flux. A small part of the magnetic flux produced by coil-1 links to coil-2. The linked flux to coil-2 induces EMF. This EMF is called mutually induced EMF.
The flux in coil-1 changes with a change in the resistance(R) value. This changing current leads change in the magnetic flux in the coil-1. The magnetic flux that is common for both the coils is the mutual flux(φm).
The strength of mutually induced EMF depends on the coefficient of coupling between the two coils.
Mutually Induced EMF Formula
The mathematical expression for mutually induced EMF is;
Where:
- em = Mutually induced EMF
- M = Mutual inductance between the coils
- dI/dt = rate of change of current
Conclusion
A changing magnetic field produces statically induced EMF in a stationary coil. It occurs in two ways—through self-induction in one winding or mutual induction between two windings.
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