[geeky geedes]

May seem trivial, but it`s a serious question!

Does a mobile phone, fully charged, weigh more than one that isn`t? I mean, energy must weigh something surely?!

Well?

[RobM]

Try it and see... Next time your battery goes flat, get the kitchen scales out and see how much it weighs. Then charge the phone and weigh it again.

Other interesting experiments could include;

Does the phone weigh less with the screen on? The light coming out of it might weigh something?

Does the phone smell nicer if I talk to a woman on it rather than a man?

Will my battery last longer if I keep my phone clean?

You could be onto something here you know!

[cokker]

Reminds me of a question I saw a couple of years ago, does a hard drive weigh more when it's full?

[Noggin1980]

While I only vaguely understand how both work I'd have thought the answer to the battery question is yes (though nothing you can tell yourself) and a tiny bit of dust on the phone will weigh significantly more and for hardrives no.

I'm sure someone will be able to give you a better answer if this is just for intellectual curiosity. Of course there is no practical difference and while I know rob is taking the mickey, nothing you could measure on kitchen scales.

[Barcoing Mad]

Yes, it does weigh more as the mass increases when it's charged. Energy has mass.

[Rygar]

While googling for an answer came across THIS old thread. Looks like this issue has been somewhat debated here before!

I'm not 100% sure of the answer but I'd guess for all practical purposes there is no difference. If there is its at the sub-atomic level and you're talking about billionths of grams.

Saw something in that old thread that made me laugh though...JagoPlasma said "after all if you pass 12v thru your arm you get buggerall"
He obviously never had a sadistic physics teacher that liked to hook up pupils to 12V powerpacks....put a decent current through one of those and the result is far from buggerall Its the volts that jolts but its the mills that kills. Strange way to teach something but I must admit I've never forgotten that fact!

[Barcoing Mad]

Let's see. My mobile battery is 750 mA hours, 3.6V. So that's 750/1000*60*60*3.6 Joules = 10 kJ roughly.

The mass increase associated with 9720 J = 1E4 /(3E8)^2 = roughly 10^-13 kg.