NEET Physics Notes Electromagnetic Induction-Self induction
Self induction
Self-Induction
- Self-induction is the phenomenon due to which an induced emf is set up in a coil or a circuit whenever the current passing through it changes. The induced emf opposes the change that causes it and is thus known as back emf.
- Inductance is the inherent property of electrical circuits and is known as the electrical inertia.
- An inductor is said to be an ideal inductor, if its resistance is zero. A capacitor is said to be ideal, if its resistance is infinite.
- An inductor does not oppose current but opposes changes (growth or decay of current) in the circuit.
Self-Inductance
Flux linked with the coil is 
where the constant L is known as the coefficient of self-induction or self-inductance of the given coil. It may be defined as the magnetic flux linked with the coil, when a constant current of 1 A is passed through it. Induced emf due to self induction
inductance of a coil/circuit is the magnitude of induced emf produced per unit rate of change of current in the circuit.
SI unit of inductance is henry. Inductance is 1 henry, if on changing the current at a rate of 1 As-1, an induced emf of 1 V is set up in the circuit.
Dimensional formula of self inductance (L) is [ML2T-2A-2].
Method of Finding Self-Inductance of a Circuit
We use the equation, 
to calculate the inductance of given circuit.
A good approach for calculating the self inductance of a circuit consists of the following steps:
- Assume that there is a current / flowing through the circuit (we can call the circuit an inductor).
- Determine the magnetic field B produced by the current.
- Obtain the magnetic flux ΦB
- With the flux known, the self-inductance can be found from
To demonstrate this procedure we now calculate the self-inductance of two inductors.
Magnetic Potential Energy of an Inductor
- In building a steady current in an electric circuit, some work is done by the emf of the source, against the
self-inductance of the coil. The work done
- The work done is stored as the magnetic potential energy of that inductor.
Thus
Formulae for Self-Inductance
For a circular coil of radius R and N turns, the self-inductance
