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RL Time Constant

Find the current-rise time constant for a resistor-inductor circuit.

Safety first, always.

ElectroLab AI teaches theory, low-voltage electronics, and planning concepts. Mains voltage, switchboards, fixed wiring, high-current systems, and legal electrical work must only be performed by licensed electricians where required.

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Visual schematic

Electromagnet coil

Current through the coil creates a magnetic field. The switch-off spike needs a safe path.

Low-voltage model
BatterySwitchCoilcoil currentFlyback diode later

TP1: coil current

TP2: switch node

TP3: coil temperature

Diagrams are simplified learning models for low-voltage electronics. They are not wiring instructions for mains, switchboards, fixed wiring, or legal electrical work.

Formula notes

tau = L / R

Inductors can kick voltage back when switched. Add flyback protection around coils.

Visual formula bench

RL current-rise view

One time constant is the first big move; about five time constants is nearly settled.

Live result

Check the inputs

tau = Check the inputs5 tau = 0.00 ms

1. Estimate

Load the example or enter a real low-voltage learning value.

2. Visualise

Use the diagram to connect the formula to current path, timing, frequency, or energy flow.

3. Verify safely

Build only suitable low-voltage circuits and confirm with a meter before scaling up.