Electrical Engineering › Section H · Magnetic circuits and inductors › Topic H.6
R-L transients
Switch a dc source onto a coil and its current does not jump; it climbs along an exponential curve set by the time constant L/R. Switch it off carelessly and the coil fights back with a voltage spike. The mathematics is the same as for capacitor charging, with current and voltage trading roles.
In this topic
- Why coil switching needs its own analysis
- The storage phase: first and last moments
- The storage-phase equations
- Worked example: switching on a coil
- Starting from a non-zero current
- The danger of simply opening the switch
- The decay phase with a discharge resistor
- Worked example: a coil switched off
- Any network: use the Thevenin resistance
- Common mistakes to avoid
- Key takeaways
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