Current rises with time constant τ=L/R.
Current in an RL circuit rises as i=(V/R)(1-e^{-Rt/L}) with τ=L/R. When switching off, the stored energy must go somewhere, so flyback diodes protect transistors. The inductor voltage jumps to oppose the change.
A 1 H coil with 10 Ω has τ=0.1 s.
The RL circuit shows how inductance slows current rise, which matters for relay drives, coils and switching power stages.
Current rises with time constant τ=L/R.
The RL circuit shows how inductance slows current rise, which matters for relay drives, coils and switching power stages.
The inductor's induced voltage opposes the rising current, so the current approaches its final value with time constant L over R.
The inductor produces a large voltage to keep the current flowing, which can damage switches, so a flyback diode or snubber is needed.
Typical applications include estimating how quickly a relay coil energises, designing the snubber for an inductive load switched by a transistor and predicting the current rise in a motor winding at switch-on.
Study "RC circuit transient" first (topic 34 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
Inductor acts open at t=0, short at ∞. Relay coil suppression. Time constant L/R.
A 1 H coil with 10 Ω has τ=0.1 s.
The next topic is "RLC circuit response", which builds directly on this one.
It is classed as Beginner in Electrical Engineering (topic 35 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
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