Self-inductance may be referred to as the resistance of the current-carrying coil against the change of current running through it. This resistance or the opposition is generated in the coil as electromotive force or EMF. In other words, the work of self-induced EMF or electromotive force is to maintain a constant flow of current through the coil. It resists the rise of the current and the fall of the current. The SI unit of self-inductance is Henry. This self inductance property of the coil is always found for the change of the current, which is the alternating current. The resistant property does not exist in direct current. “L” represents inductance. 

Some factors responsible for self-inductance are cross-sectional area, the number of turns of the wire the coil consists of, and the permeability of the material used in the core. The formula for self-inductance is 

e = -L (di/dt)

Here L is the inductance of the coil, i is the current passing in the coil and dt is the small time period.

Inductor

An inductor may be defined as a circuit element that possesses the property of inductance. A coil of copper wire is one of the best examples of an inductor. In other words, the inductor is an electrical device with two terminals for current flow through it, and it performs the task of storing energy in the form of a magnetic field when an electric current flows through it. It is also known as the coil, chokes, or reactor. 

Lenz’s law

Lenz’s law helps determine the direction of an induced current. According to this law, the direction of an induced current is such that it resists any change in the magnetic field that induced the current. This law has much importance in understanding the properties of inductive reactance.

Inductive reactance

An element’s inductive reactance may be defined as reducing the current flow in any circuit generated by induction.

Self-inductance of a solenoid

A solenoid is an electromagnet that comprises a coil of wire, a housing, and an armature. A strong magnetic field is created when electric currents pass through the coil’s wire. The housing of solenoid, made of iron or steel, surrounds it. Solenoid converts the electric energy into magnetic energy.

Let us discuss in detail how a solenoid works:

  • The solenoid coil is made up of copper wire rounded in many turns. When the electric currents pass through it, a magnetic field is created. 
  • The solenoid housing, made up of iron or steel, surrounds the coil concentrating the magnetic field already generated in the coil.
  • The armature has the task of stopping it through the concentration of the magnetic field, which provides mechanical force for doing such.
  • Thus, we can say that solenoid is a device that produces a controlled magnetic field throughout the coil.

The mutual inductance

The mutual inductance is produced in more than one coil. It can include a primary coil and a secondary coil. Like self-inductance, the resistance or opposition is produced in the coil itself, but it is produced mutually.

When two coils are kept close to each other as primary and secondary coils, a battery and a key connect to the primary coil. In contrast, we connect a galvanometer to the secondary coil across the primary coil. When a change in the current or magnetic flux occurs linked with the primary coil, then in the secondary coil, an EMF ( electromotive force ) is produced in opposition to this change. This process is known as mutual inductance. 

Let us discuss how the mutual inductance takes place in detail: 

  • The mutual inductance possesses the characteristics of a pair of the coils used. The characteristics of primary and secondary coils will be derived in mutual inductance. 
  • During mutual inductance, resistance or opposition produced in the neighbouring coil resists its decay as the primary current decreases.
  • Likewise, the resistance developed in the neighbouring coil resists the increase of the currents in it when the primary current in the coil increases.
  • Thus, we can say that in mutual inductance, the change of the current in one coil produces the electromotive force in its neighbouring coil. The strength of the EMF generated here will depend on the mutual inductance of the coils being used. Like self-inductance, the SI unit of mutual inductance is also Henry.

Conclusion 

Thus, we can conclude that self-inductance is one of the properties of an inductor or a coil. It resists the change in the current flowing through the inductor when a current is induced in it. It opposes the increase in current through the coil when the primary current increases, and it opposes the decay in the current of the inductor when the primary current decreases. The resistance generated in the inductor or coil is EMF or electromotive force. Some laws regarding self-induction, such as Faraday’s laws and Lenz’s law, give us the proper understanding of the properties of self-inductance, eddy currents, or electromotive force. Lenz’s law is concerned with the direction of an induced current in the coil, which is very important to understand. When self inductance is produced in more than one coil, it is known as mutual inductance. Two coils are involved in mutual inductance, primary and secondary coils. The properties of characteristics of mutual inductance depend on the properties of both the coils being used in it.