power measurement

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#1 21664997 30 Nov 2012 07:41

Dixit Patel Dixit Patel

Anonymous

Post #1
21664997 30 Nov 2012 07:41

I have nokia 5233 charger which shows

Input - AC 100-240 V / 50-60 Hz / 125mA

Output - DC 5 V / 890mA

then how can i calculate power used by it in one hour?? Is there use of equation P=VI but what about time???
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#2 21664998 30 Nov 2012 08:49

Peter Evenhuis Peter Evenhuis

Anonymous

Post #2
21664998 30 Nov 2012 08:49

you are providing design numbers and not real numbers.
Yes 5V output is 5V output.
The 890mA is a maximum in real life this is lower and only during charging.

And yes DC power is P=VI
So when you measure the real current you can calculate.
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#3 21664999 30 Nov 2012 08:51

David Adams David Adams

Anonymous

Post #3
21664999 30 Nov 2012 08:51

so useage would be W-H or W-sec or W-m. Just be aware of the units you work with. Most people use KWH but your useage will be small - so I would recommend W-H so Watt Hours = P*t

as an example 5V * 890mA * 1H = 4.45 watt hours or divide by 1000 and you would get .00445 Kilowatt Hours
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#4 21665000 30 Nov 2012 09:20

Dixit Patel Dixit Patel

Anonymous

Post #4
21665000 30 Nov 2012 09:20

thx...
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#5 21665001 30 Nov 2012 09:23

Dixit Patel Dixit Patel

Anonymous

Post #5
21665001 30 Nov 2012 09:23

thx...i completly understand....thanks a lot..
#6 21665002 30 Nov 2012 11:23

Earl Albin Earl Albin

Anonymous

Post #6
21665002 30 Nov 2012 11:23

Look up the definition of power and the units, then look up the definition of energy and then units. It's all defined.
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