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Q & A: dimming LEDs

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Most recent answer: 08/05/2013
Q:
when a Motor and an LED are connected in parallel combination with each other and entire combination with a constant potential source , then why does the LED glows less brightly when both devices are switched on as compared to the case when it glows brighter when only LED is switced on with the same potential source
- Sanidhya Khajuria (age 15)
jammu J&K INDIA
A:

Since the current through the LED is determined by the voltage across it, it seems that connecting the motor in parallel is reducing the voltage. The "constant potential source" isn't quite constant.

Mike W.

One of the reasons that the battery voltage is reduced is that all batteries have an 'internal restance'.  For a 9 Volt battery drawing 1 Amp the actual terminal voltage will drop a half a Volt or so.  This voltage drop will dim the LED.

LeeH


(published on 08/05/2013)

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