LR Time Constant Calculator

Calculate the time constant (τ) of an LR circuit, which represents how quickly the current reaches approximately 63.2% of its final value during charging or decays to approximately 36.8% of its initial value during discharging.

Input Parameters

Calculation Results

Calculation Formula

τ = L × R

Where:
τ = Time Constant (seconds)
L = Inductance (Henrys, H)
R = Resistance (Ohms, Ω)

LR Time Constant Calculator Usage Guide

Learn how to use the LR Time Constant Calculator and understand its applications in electrical engineering

What is the LR Time Constant?

The LR time constant (τ) is a characteristic of an RL circuit that determines how quickly the current in the circuit responds to changes in voltage. It represents the time required for the current to reach approximately 63.2% of its final value during charging or to fall to approximately 36.8% of its initial value during discharging.

How to Use This Calculator

  1. Enter the inductance (L) of your circuit in Henrys (H). This is the measure of the electrical device's opposition to changes in current.
  2. Enter the resistance (R) of your circuit in Ohms (Ω). This represents the opposition to current flow in the circuit.
  3. Click the "Calculate" button to compute the time constant.
  4. The result will be displayed in seconds (s).

Practical Applications

The LR time constant is crucial in various electrical applications:

  • Switching circuits and relay timing
  • Filter design in electronic circuits
  • Inductive load control in power systems
  • Motor starting and protection circuits

Example Calculation

For a circuit with an inductance of 5 Henrys and a resistance of 100 Ohms:

τ = L × R = 5 H × 100 Ω = 500 seconds

This means it will take approximately 500 seconds (about 8 minutes and 20 seconds) for the current to reach about 63.2% of its maximum value when the circuit is powered on.