Would you swap food for USB charging?

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Offline thedoc

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Would you swap food for USB charging?
« on: 28/07/2015 19:27:13 »
If a human could be fed with energy via USB ports rather than food (like the synths in Channel Four's 'Humans) how long would it take to fully charge an average human with, say, 2000 calories of energy?
Asked by Aaron Fuller

                                        Visit the webpage for the podcast in which this question is answered.
[chapter podcast=1001104 track=15.07.28/Naked_Scientists_Show_15.07.28_1003931.mp3]  ...or Listen to the Answer[/chapter] or [download as MP3]
« Last Edit: 28/07/2015 19:27:13 by _system »

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Offline alancalverd

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Re: Would you swap food for USB charging?
« Reply #1 on: 29/07/2015 12:45:47 »
2000 Calories (capital C = kilocalories) is about 10 megajoules.

If you USB port delivers 5 volts then it will take 2,000,000 ampere-seconds to deliver 10 MJ. A 10 amp USB charger will thus require 200,000 seconds or 56 hours to recharge a human.

However most of the 2000 Calories you eat each day, is used to keep your body at its working temperature. If you were replaced by an entirely electrical system to do the same amount of useful work, you could be recharged in 2 or 3 hours.
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BobonToast

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« Reply #2 on: 29/07/2015 14:12:46 »
I think that should be 8 million divided by 15 (not 4200)?