# How is voltage exactly created in a citcuit? [duplicate]

I just began studying electricity and concept of voltage and this particular concept of voltage is so confusing. I have searched answer for this question everywhere and every answers stops short at saying that voltage is created by chemicals in a battery and nothing beyond this. You don't need to go deep into explaining chemistry but I just need an idea of how electric potential is created in batter and how it "forces" electrons in circuit to move. Like how is charges spearate in first place. If battery is not one to supply electrons in first place, then how come potential difference is created in battery which would then force electrons in wire to flow. If anyone can shine light on this, I really appreciate it.

• Recharging a rechargeable battery is a bit like using an electric winch to drag a boulder up a hill, and then rolling it back down with the winch line attached to a generator... Jan 19 '17 at 13:13

You should start from a physics course. Learn what charge is, what is electric field, what is electric potential.

Basically negatively charged particles are attracted to positively charged particles. So if you have them separately, they will flow one to another and release some energy in the way.

Circuits are just engineering of physics. Chemical reactions in battery separates atoms to ions (positive charge) and electrons (negative charge), while wires allow them to flow.

Physics won't give you a 'why' answer, but it can give a 'how', or a 'sort of like this', if you're happy to think in terms of lower level things that can't themselves be explained.

Taking your specific case of a chemical battery. A battery is two different conductive materials (electrodes), separated by an ionic fluid (electrolyte). For instance a zinc plated nail and a copper coin pushed into a lemon makes a battery. This battery operates by exactly the same principles as any other.

The electrodes will tend to dissolve in the electrolyte to different extents. Solution involves the movement of some of the electrons on atoms to make ions. Some atoms hold tight to their outer electrons, some less so. This difference makes for a difference in the energy that is released or absorbed when atoms go in or out of solution, and also makes for a difference in the number of excess electrons (charge) that appears on each electrode as it reaches equilibrium with the electrolyte.

You can think of the different charges on the electrodes as causing a different 'pressure' of excess electrons. Some languages in fact use the word 'pressure' for voltage. If the electrodes are connected by a wire, this voltage difference causes electrons to flow along the wire.

More strictly, voltage is a measure of how much energy is involved when charge moves. You can see that this energy is intimately related to the difference in the energy of solution of the different electrode materials.

A lemon battery works, but does not work well. Most of battery technology is about finding electrodes with a large energy difference, that are cheap to make and practical to build into a battery, hence lead, nickel, lithium, and electrloytes that work well with them.

The voltages in a circuit are (usually) there because the circuit needs to be powered for it to work.

Maybe your question is more like: many circuits generate their own internal voltages. Especially many power supplies generate for example 5 V. How do they "know" what 5 V is ?

Although as explained in the other answers, certain chemical reactions like used in batteries result in a certain voltage. But as batteries wear out and may contain nasty chemicals, this is not a very practical way to generate a specific voltage. Also that voltage changes a lot over temperature and lifetime and charge level of the battery.

So instead most circuits use a special circuit as a reference, that circuit is called a bandgap reference circuit. It uses the physical properties of diodes and/or transistors to generate a (fairly) constant voltage. Such a circuit is used in almost every voltage regulator circuit and other circuits where a reference voltage is needed.

Using voltage divider circuits (consisting of just a couple of resistors) and amplifiers that bandgap reference voltage can be reduced or amplified to practically any value needed.