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Capacitors in cars

  1. Jun 26, 2012 #1

    Does anyone know which parts of an automobile would require the use of capacitors?

    Also, what kinds of capacitors are used in this case? (aluminum, tantalum, ceramic, ??)

    Many thanks!!!
  2. jcsd
  3. Jun 26, 2012 #2


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    In locksmith college, back in '79, we were taught that we have to disconnect the battery at least 11 minutes before pulling the steering wheel in order to let the airbag trigger "bleed down". I assume that caps are involved in that. No idea what kind.
  4. Jun 26, 2012 #3


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    Capacitors are often used in cars for ignition noise suppresion.
    on older cars you will find one in the distributor.
    Capacitor Discharge Ignition units with have a couple
    in more modern cars you will find lots of capacitors in the Engine Management Computer systems.

    The suppression ones will generally be non electrolytic ~ 1 uF give or take a bit
    CDI's and EMC's will likely to have a mix of types

  5. Jun 26, 2012 #4
    A capacitor is placed across the 'points' in the ignition system to enable a spark of sufficient duration to be generated
  6. Jun 27, 2012 #5
    Hybrid cars use relatively large capacitors in the inverter module. I don't know what kind they are but compared to other capacitors I've seen they're freakin' huge. The size of soda bottles.
  7. Jun 27, 2012 #6
    The alternator is a belt-driven AC generator. That AC is fed to diodes that convert it to DC. The DC that comes out of a rectifier is very wiggley. A parallel capacitor eliminates a lot of the ripple on that DC level, by making use of the old rule that the voltage across a capacitor can't change any faster than charges can be physically moved onto or off of its plates (Q=CV).
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