[SOLVED] basic power and energy requires solution

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p.mahen

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The main aircraft battery is used to start an engine. If the starter demands a current 1000A for 30 sec. and the battery voltage remains at 12V during that period, determine the amount of energy required to start an engine.
 

by definition energy is integral of v*i in time domain.
 

p.mahen said:
The main aircraft battery is used to start an engine. If the starter demands a current 1000A for 30 sec. and the battery voltage remains at 12V during that period, determine the amount of energy required to start an engine.
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Its hard to tell without measuring, the same situation like in cars.

We dont know local resistance on battery contacts and resistance of wires. Even small resistance of 0,05-0,1Ω can decrease current and starter will receive smaller amount of power.


But theoretically (P = V * I) gives you power, and if you include time in that you will get amount of power (KW/h, W/h, ...).




Best regards,
Peter
 

V * I * t = 12 * 1000 * 30 = 360,000 joules

It is better expressing this result as Wh (Watt-hour) or KWh.
 
Last edited:
In your model its around 0,1KW/h or 100W/h.

12V x 1000A = 12000W * (30/3600) = 100W/h

Amount of energy is equal like when one bulb of 100W works 1h.



Best regards,
Peter
 
Thanks for the solution.
It really helped

- - - Updated - - -

Thanks for all
 

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