Name: Self Induction
Uploaded: 2019-07-19
Duration: 5 min 48 s
Description: This video describes the principle of self induction. It defines self-inductance and gives the formula for the same and derives its SI unit as well.

Question

What is self induction? Write the unit of self inductance? Derive an expression for energy stored in current carrying coil.

Accepted Answer

Self-inductance of a coil is defined as the ratio of the total flux linked with the coil to the current flowing through it.

Its unit is henry.

$L = INϕB$

When the current is varied, the flux linked with the coil changes and an e.m.f. is induced in the coil. It is given as

$ε = - \frac{d (NϕB )}{dt} = - L \frac{dI}{dt}$

The self-induced e.m.f. is also called back e.m.f. as it opposes any change in current in the circuit.

So, work needs to be done against back e.m.f. in establishing current. This work done is stored as magnetic potential energy. The rate of doing work is given as

$\frac{dW}{dt} = ∣ ε ∣ l = LI \frac{dI}{dt}$ (neglecting negative sign)

Thus, the total work done in establishing current from $0$ to $1$ is

$w = \int dW = \int_{0}^{1} LIdI = \frac{1}{2} {LI}^{2}$

What is self induction? Write the unit of self inductance? Derive an expression for energy stored in current carrying coil.

Important Questions on Electromagnetic Induction

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