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Glossary of terms you will come across during your Phase 2 training.

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To quench a flame means to put it out. For example, you would use a fire extinguisher to quench a fire.

In the context of combustion in an engine, quenching means that when atomised fuel enters a cold engine, the low temperatures cause the atomised fuel particles to condense on the relatively cool cylinder walls.

As we know, the only part of any fuel that burns is the vapour, so fuel that has condensed on to a cold cylinder wall does not produce vapour and will not burn.

The areas around cylinder walls are known as quenching zones, and any fuel in these zones will not burn. On the exhaust stroke, this unburnt fuel is expelled from the engine as HC (hydrocarbon).


Represented in datasheets with the abbreviation Iq, quiescent current is the current used by a device when it is ready to operate, but not yet supplying any current to a load.

You can think of quiescent current as the current required have a device ready to perform a task, but not yet performing that task.

You could also think of it as the current used by a component when it is powered up, but not yet operating.