Inductive time constant

Definition

The inductive time constant, denoted as $\tau_L$, is the time required for the current in an RL circuit to change significantly (about 63.2%) towards its final value after a change in voltage. It is calculated as $\tau_L = \frac{L}{R}$, where $L$ is the inductance and $R$ is the resistance.

5 Must Know Facts For Your Next Test

1. The inductive time constant quantifies how quickly current changes in an RL circuit.
2. $\tau_L = \frac{L}{R}$, with units of seconds (s).
3. A larger inductance or smaller resistance results in a larger time constant.
4. After a period of about $5\tau_L$, the current reaches over 99% of its final value.
5. It plays a crucial role in determining the transient response of RL circuits.

Review Questions

• How is the inductive time constant ($\tau_L$) calculated?
• What effect does increasing the resistance have on the inductive time constant?
• After how many time constants does an RL circuit reach near its steady-state current?

Related terms

Inductance:

Property of a conductor by which a change in current creates an electromotive force (EMF), measured in henries (H).

RL Circuit:

An electrical circuit consisting of resistors (R) and inductors (L) driven by a voltage source.

Transient Response:

The behavior of an electrical circuit immediately after a change in voltage or current before reaching steady state.