If my phone is charging that means it's mass increasing by this Youtube video.

Now if an current is flowing from the power station to home, does it mean that electron is flowing from house to the power station (on the basis of convectional direction of current)? And the house is losing some amount of mass?

  • $\begingroup$ First off, the electron does not flow from power station to house. Because it is alternating current, the electrons stay more or less in one spot and vibrate back and forth. Second, the video does state that charging you cellphone makes it gain weight, but if that is true, consider then that your cell must lose that weight by the time the battery is drained. Where does it go? it would go to the environment; your house. But I would argue that by nature of being a closed circuit and grounded, no mass is actually gained or lost by your house. $\endgroup$ – Jim Aug 8 '13 at 15:55
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    $\begingroup$ @Jim Although the electrons aren't going anywhere (I hope), energy is added to the system when charging, and this energy is sent back out into the environment when using the phone (sound, light, heat, EM radiation for the radio). Energy is mass, be it very little mass. So the phone's weight does actually change. Although the accumulation of dust on the phone might be more significant... $\endgroup$ – JSQuareD Aug 8 '13 at 21:31
  • $\begingroup$ @JSQuareD notice I never said the phone doesn't gain or lose weight. I said your house wouldn't. $\endgroup$ – Jim Aug 9 '13 at 14:03
  • $\begingroup$ @Jim In that case, I agree with you :) $\endgroup$ – JSQuareD Aug 9 '13 at 19:01

The charging current warms the battery as it charges, and because of mass-energy equivalence, an unmeasurably small amount of mass is indeed added to the phone in the process. However, this is not what is measured by your electric utility in order to bill you for energy.

The insignificant mass added to your phone when charging is lost partially when the heat from charging the battery radiates away, and also is diminished whenever the phone is actually in use, in either transmit or receive mode.

On the way to your home phone charger from the power station, a very small amount of energy of the electrons is also lost by heating transmission lines and transformers as the energy they carry is transferred.

The conventional direction of current flow is just that: a convention. It doesn't mean that the positive charges in the wires need to have a net flow into your home, or even that the same electrons that left the power station need to be deposited in the wires at your home in order for an electric current to flow. All that is really necessary is for the energy of the electrons at the power station to push the electrons in the wires in the direction of the electrical consumer's house, and as this is done with alternating current (50 or 60 Hz), no net deposition of mass, particularly electrons, needs to happen anywhere in the process.


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