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Hello I am new to electronics. I read electricity works this way - some atoms have more electrons than protons. These free electrons flow through a conductor such as a copper wire. However, to induce flow of electrons we need a source to push the electrons such as a battery.

Does this mean the free electrons from the conductor itself (copper) flow or does that mean electrons inside the battery flows?

(If free electrons from the copper flow, wouldn't copper run eventually run of its' free electrons?)

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"some atoms have more electrons than protons" - such atoms are called ions and they are what what conducts electricity in water. – Ivan Mar 2 '14 at 5:36

some atoms have more electrons than protons?

No, they have the same number but some of the electrons have more freedom to move.

Does this mean the free electrons from the conductor itself (copper) flow?

Yes. They jiggle about randomly relatively fast (~2 x 10^6 m/s). In the presence of an electric field, they very slowly drift in one direction ( ~1 m/h).

wouldn't copper run eventually run of its' free electrons?

No, as many are added at one end of a piece of copper as are lost at the other end.


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free electrons are present both in conductor and source.These electrons are only drifted by the potential difference across the voltage source. That means electrons are circulating in a closed loop, so the number of electrons flowing out of the conductor is equal to the number of electrons entering the conductor. So as you think the conductor wont run off its free electrons.

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If you're happy with circuit powered by a battery then what happens in that situation is that there are "free" electrons produced by the chemical reaction at the negative plate. At the positive plate, a chemical reaction cannot occur because in order for it to occur, "extra" electrons are required. In a lead-acid battery, the number of electrons produced at the negative terminal is exactly the number needed by the positive terminal.

This "need" is really an electric field. The "need" at the positive plate "pulls" the "free" electrons from the negative plate through the copper wire so that it can complete a chemical interaction.

Disclaimer: Quotation marks are used to indicate that some liberty is being exercised for purposes of demonstration.

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Good curiosity! Sometimes people don't think about how the electricity travels as long as their circuit works but most Professional Engineers or hobiest would know this for sure.

Electricity flows with Voltage (energy of electrons or charge as charge is directly proportional to #of electrons). The copper is just a medium that allow electrons to move freely. It is the battery that is the source of electrons and holes otherwise battery would not have been called a source! So, the chemical reaction inside a battery generate cations and anions that are generated at two terminals "+" and "-". As long as they are connected through your circuit electrons and holes find a path to travel. An electron from a battery terminal doesn't necessarily have to flow from "-" end to another end of the "+ " terminal but think of them as like a series of electrons in a line (the motion is quite shattered inside bad conductors but pretty smooth and conductive in copper wire) push each other. Same thing with holes but in reverse direction, as absence of electron is hole.

So, depending on the voltage (which depends on intensity of chemical reaction inside a battery) and the circuit impedance, number of electrons/holes travel through copper. That electron might be belong to the copper or the battery as they tend to push each other to create a electron motion. Remember, electron travel speed is much slower (as they just have to hit and pass the energy to next electron) than the motion created by the real electricity.

After a long consumption of charge, the chemical process inside a battery slows down and therefore, the energy in your charge is less so, less force to push electrons and thus your battery starts giving lower voltage than its regular voltage.

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