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Q & A: battery voltage and power

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Most recent answer: 01/20/2017
Q:
I teach 4th grade, and every year the students create quiz boards. We use Christmas tree lights for the light. Previous years we only needed 1 'D' or 'C' battery to light the bulb. This year the Christmas tree lights were LED, and we discovered you needed 2 batteries to light the bulb. If LED lights use less energy, why did we need more power (batteries) to light them?
- Molly (age 41)
Fishers, IN, USA
A:

It seems that your LED's need ~3V to work, which is typical. That doesn't mean that they use more power than  a similarly bright incandescent bulb. The power (rate at which energy is supplied) is the product of the voltage and the current. Your LEDs are drawing much less current than incandescent lights with similar brightness. The batteries will last much longer.

Mike W.


(published on 01/20/2017)

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