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The Unit of Inductance

<^< Examples: Capacitance | Course Index | Flux Linkage and Current >^>

Inductance is the property of a coil which gives rise to the opposition to a change in the value of current flowing in it. Any change in the current applied to a coil/inductor will result in an induced voltage appearing across it.

The unit of inductance is the henry (H) and a coil is said to have an inductance of 1H if a voltage of 1V is induced across it when a current changing at the rate of 1A/s is flowing in it.

The voltage induced across the terminals of an inductor will thus be proportional to the product of the inductance and the rate of change of applied current. Hence:

e = - L x (rate of change of current)

(Note that the minus sign indicates the polarity of the voltage, i.e. opposition to the change).

The rate of change of current is often represented by the expression di/dt where di represents a very small change in current and dt represents the corresponding small change in time.

e = - L (di / dt)

Current increasing at 0.01 As-1 Current increasing at 0.1 As-1 Current increasing at 1 As-1 Current increasing at 10 As-1

0.01 A/s 0.1 A/s 1 A/s 10 A/s

<^< Examples: Capacitance | Course index | Flux Linkage and Current >^>