Induction

Overview

Engineering reference data for Induction in electrical engineering.

Key Formulas

Ohm's Law

$V = IR$

Voltage = Current × Resistance.

Power

$P = VI = I^2R = V^2/R$

Electrical power.

Energy

$E = Pt$

Energy = Power × Time.

Variables

Symbol	Description	Unit
$V$	Voltage	V
$I$	Current	A
$R$	Resistance	Ω
$P$	Power	W

Example Calculation

A coil with 500 turns experiences a change in magnetic flux of 30 mWb over 30 ms. The induced EMF is calculated as:

$$\text{EMF} = -n \frac{\Delta \Phi}{\Delta t} = -500 \times \frac{30 \times 10^{-3}\ \text{Wb}}{30 \times 10^{-3}\ \text{s}} = -500\ \text{V}$$

The negative sign indicates the direction of the induced EMF opposes the change in flux (Lenz's Law).

Important Note on Coil Inductance Formula

The empirical formula for the inductance of an air-filled cylindrical coil:

$$L = \frac{\mu_0 n^2 A}{l + 0.45d}$$

is valid only when the coil's length $l$ is greater than half its diameter $d$ (i.e., $l > 0.5d$).

References

• Original Source