How To Cook an Egg with Mobile Phones

[Kingfisher]

How To Cook an Egg with Mobile Phones

haa ???

I was really amazed to see this !!

[Christopher Tidy]

Something ain't right. I reckon that egg was pre-cooked.

I'm bored, so I thought about this in some more scientific detail.

My old mobile phone has a battery marked 4.8 V, 650 mAh. So the power available from the battery is 4.8 * 0.650 = 3.12 W (even though it might not be healthy to discharge the battery this quickly). In an hour that adds up to 3.12 * 3600 = 11232 J of energy. Suppose an egg weighs 50 g and has the same specific heat capacity as water. So its heat capacity is 0.05 * 4180 = 209 J/C. Suppose that the egg needs to be heated to 100 C to cook it, and that room temperature is 20 C. That requires an energy input of 80 * 209 = 16720 J. That is more than is stored in one phone battery. Okay, it's not more than is stored in two, but for two phones to throughly cook the egg it would require that (i) the phone batteries were almost completely discharged by an hour's worth of use (possible), (ii) that almost all the energy from the batteries was converted to radiation (unlikely), and (iii) that almost all the radiation was absorbed by the egg (not possible, as it will be spread pretty evenly by the aerial, so most will miss the egg). It would require an extremely efficient system in order for phone batteries to cook an egg. So I'm convinced the story is false.

I was bored :-D.

Chris

[Dave Fawthrop]

On Thu, 15 Jun 2006 17:54:25 +0000, Christopher Tidy wrote:

|Kingfisher wrote: |> How To Cook an Egg with Mobile Phones |> |>

|> |> Cool haa ??? |> |> I was really amazed to see this !! | |Something ain't right. I reckon that egg was pre-cooked. | |I'm bored, so I thought about this in some more scientific detail. | |My old mobile phone has a battery marked 4.8 V, 650 mAh. So the power |available from the battery is 4.8 * 0.650 = 3.12 W (even though it might |not be healthy to discharge the battery this quickly). In an hour that |adds up to 3.12 * 3600 = 11232 J of energy. Suppose an egg weighs 50 g |and has the same specific heat capacity as water. So its heat capacity |is 0.05 * 4180 = 209 J/C. Suppose that the egg needs to be heated to 100 | C to cook it, and that room temperature is 20 C. That requires an |energy input of 80 * 209 = 16720 J. That is more than is stored in one |phone battery. Okay, it's not more than is stored in two, but for two |phones to throughly cook the egg it would require that (i) the phone |batteries were almost completely discharged by an hour's worth of use |(possible), (ii) that almost all the energy from the batteries was |converted to radiation (unlikely), and (iii) that almost all the |radiation was absorbed by the egg (not possible, as it will be spread |pretty evenly by the aerial, so most will miss the egg). It would |require an extremely efficient system in order for phone batteries to |cook an egg. So I'm convinced the story is false.

Don't confuse the idiots with facts. They believe the silly stories.

[MatC]

Did'nt anyone watch Braniac? (Sky One - Richard Hammond Presented it) They do a section called "I Can do Science, Me" - And they tried it then, with loads of mobiles (50 or 100), and that did'nt work....

Mat

[Guy King]

The message from "MatC" contains these words:

Thing is, you shouldn't need to try the experiment. The energy density of a phone battery isn't great, mine's a 800mAh at 3.7V - 3600x0.8x3.7 - a little over 10kJ.

Let's say an egg weighs 50g and is mostly water. The SHC of water is around 4J/g/K so to raise 50g by the 80 or so K it takes to boil it would be 50x4x80=16kJ. So, even a big phone battery, which might hold more charge may still only have roughly enough energy contained in it to boil just the egg, but that presupposes most of the energy actually gets to the egg. If the electronics waste 50% and the egg's not 100% efficient at catching it, and unless the egg completely surrounds the phone we're going to be a couple of orders of magnitude out.

And, of course, to do it uninsulated for four minutes....