10

I have read this:

the definition of electrical current is the flow of charge. Now, it is also possible to transfer energy (and therefore power) through either free space or a conductor by electromagnetic fields. This does not require any charge carriers to move from one to the other, and indeed moves much faster than the charge carriers.

Is electric current actually the flow of electrical charge?

Now if I connect the battery to a traditional (wired) charger, I connect it to the power outlet, the power network that provides electricity (defined as the flow of electrons or any charge carriers), that is, my depleted battery will receive a flow of electrons, and charge up. Though, the wireless charger should not be able to do that.

In other words, does the charged up battery have more electrons than the depleted one (since the traditional/wired charger transfers electrons from the network to the battery)?

Question:

  1. How does a wireless charger work if there is no transfer of electrons?
Qmechanic
  • 220,844
Árpád Szendrei
  • 30,008

3 Answers3

24

The time-varying magnetic field created by the wireless charger induces an electromotive force in the wireless charging coil of the device. This electromotive force (after being rectified) drives electrons from the positive terminal of the battery to the negative terminal, reversing the chemical reaction and recharging the battery.

Due to charge conservation, electrons are neither created nor destroyed in a battery. The discharging of a battery involves a spontaneous redox reaction which decreases the Gibbs free energy of the system. Electrons are simply moving from a higher-energy state to a lower-energy state within the device. The difference in energy is used to power the device, much like how the (gravitational potential) energy of rivers is harvested through hydroelectricity. Recharging the battery simply uses an external force to move them back to the high potential. The net charge is always zero. Therefore, external electrons are not necessary.

Vincent Thacker
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15

Does the charged up battery have more electrons than the depleted one ?

No. A charged battery has exactly the same amount of electrons as a depleted one. It is just that the electrons in the charged battery are at a higher potential. The charged battery can then send these high potential electrons around a circuit to do work by running motors, lighting LEDs etc. etc. When they have done this work, the electrons (now at a lower potential) return to the battery.

A traditional battery charger pushes high potential electrons in at one end of the battery and removes the same amount of low potential energy electrons from the other pole of the battery. A wireless charger does the same thing using electromagnetic waves to move the electrons.

gandalf61
  • 63,999
4

You can think a wireless charger is similar to a power transformer where the primary coil is in the charger and the secondary is inside your device, including the necessary rectifier. Wireless charging works only on short distance, the closer the better, for efficiency.

Ulrich Roos
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