# Electrons moving in a simple circuit with a battery and a light bulb

I believe my understanding of electric currents is flawed and want some help to clear up a few things. I'm not looking for a precise scientific understanding, but to understand the basics. I'll try to explain my understanding instead of asking a bunch of questions but if I should boil this down to one question only, that would be how the energy is transferred from the battery through the electrons and into heat making the lightbulb glow? I know the explanation below is very simplified, but is it simply wrong? (English is not my first language)

Let's think of a simple circuit consisting of a battery, conductors and a light bulb. I know batteries are very varied, but to simplify a lot we can think of the minus-pole of the battery consisting of electrons being "released" into the conductors, this causing the voltage drop to occur. This causes the electrons in the whole network to bounce into each other, repel each other and being "driven" towards the plus-pole, I guess both because of negative electrons repelling each other and later them being attracted to the positive particles in the plus-pole. The energy, which makes the lightbulb glow, is the kinetic energy of the electrons, started by the battery introducing the voltage. This energy will be transferred to heat (at least in older lightbulbs (because of resistance in the thin wire in the bulb?)) causing the lightbulb to glow.

The battery is an energy source that supplies the electrical energy to the electrons in the conductors. There is no actual flow of electrons. It's the energy that is transferred. A conductor contains large no. of atoms tightly packed with plenty of availability of valence electrons that are ready to move out from the atom if you supply a little bit of energy. Once the energy is provided from a battery, the electrons accepting that energy get accelerated because of that field. But it's velocity will get averaged due to increased amount of collisions with the atoms. So the resulting velocity get averaged. If it;s the flow of electrons that make the bulb glow, then due to the average velocity of the electrons, it take a finite time to make the bulb glow after the switch is on. But in reality things happen in a different way. Switching on and the glowing of bulb happens at the same instant. So, the principle is something different. The electrons accepting the energy will move forward and come in the vicinity of another electron. This increases the potential energy of the system. The second electron transfers this potential energy into kinetic energy and move forward. So there is electron movement. But the electrons are just carriers of energy. They just transfer the energy from electron to electron. Now a bulb has some resistance. So the electrons will lose some energy there which appears as heat and makes the filament glow.

I try to think of everything in terms of chemical potential. Many batteries utilize lithium ions to create a chemical gradient. This creates a driving force across the circuit, called voltage.

Keep in mind that the electrons are not moving that quickly - it acts more as a wave travelling through. If you are interested, you can learn more about the actual velocity of the electrons - called "drift velocity" - here.

In the classical orbital model, resistance can be described as collisions between electrons. As the high-energy electron wave slams through the relatively less-excited electron sea, the collisions generate temperature increase.

All materials have an associated resistance (unless they are a superconductor at an appropriate temperature) and will generate collisions. The number of collisions is proportional to the severity of the chemical gradient (voltage). Think of a resistor as an obstacle course, where the electrons need to run through. The type of material will change the difficulty of the course. Also, independent of material, a longer obstacle course is harder, while a wider obstacle course is easier.

If you want to look more into circuits, I would recommend starting with Ohm's law, then moving onto Kirchoff's laws.

A filament of a light bulb can be thought of as being composed of a lattice of positive metal ions which are vibrating about fixed positions and a sea of mobile electrons which are responsible for the metal being an electrical conductor.

With no external circuit present a chemical process within a battery moves mobile electrons within the battery to produce a surplus of electrons on the negative terminal and a deficit of electrons on the positive terminal. These charges produce an electric field inside the battery which eventually opposes the movement of further electrons between the terminals. You can imagine the battery as something which pumps mobile electrons from the positive terminal to the negative terminal.

When an external conducting circuit (wires and bulb) is connected to the terminals of the battery an electric field is produced in the external circuit.
Due to that electric field the mobile electrons in the external circuit are accelerated and gain kinetic energy.
Whilst gaining kinetic energy the mobile electrons "collide" with the vibrating lattice ions and transfer some of their kinetic energy to the lattice ions.

The net effect is that the mobile electrons gain kinetic energy from the electric field produced by the battery which was produced by the chemical reaction in the battery using chemical energy. The mobile electrons travel around the circuit transferring kinetic energy to the lattice ions and make them vibrate more, ie increase their temperature. The filament has been "heated".

The mobile electrons suffer less collisions in the wires and so the wires are "heated" less than the bulb filament. The wires have a much lower resistance than the bulb filament.

Okay, it's partially wrong. A battery is a device that maintains a constant potential difference between its terminals (generally through chemical stuff). Circuits are conductors. Conductors have electrons that can easily flow across their atoms. It's like conductors have a "sea" of electrons. The potential difference causes the circuit's electrons to move in the direction of the positive terminal and then the battery does work to "pump" them to the negative terminal. The electrons just circle around the circuit. The battery does not generate new electrons! A light bulb is a resistor, so yes, the electrons' energy is transferred to the filament in the bulb and the temperature causes the bulb to glow.

• I realize the battery does not create electrons, but would it be wrong to say it contain a majority of electrons in the minus pole , and when being part of a circuit will add to the potental difference as they're constantly "pumped" back towards the minus pole avoiding equilibrium? Apr 17, 2016 at 21:32
• Yes, I'm quite certain that statement is wrong. I'll admit to not being a PhD, but I'm a second-semester honors physics student who just finished the electricity and magnetism part of his course and has moved on to special relativity. I'm aiming for a PhD. Just so you know who you're getting this from. If that statement were true then I think I would most likely know about it.
– user113773
Apr 18, 2016 at 4:22
• Thanks a lot for your feedback. Just to make sure we're not misunderstanding each other, a visual presentation of my thoughts would be something like this: element14.com/community/servlet/JiveServlet/showImage/… So this is wrong? Apr 18, 2016 at 10:01
• Okay, when you wait a while, the electrons won't end up bunched up, they're more or less ALL traveling at a constant speed called the "drift velocity". Yes, the resistor makes electrons bunch up, but only temporarily. The "long term" (it's happens pretty quickly I believe) effect of a resistor is the electrons all moving slower BUT AT THE SAME SPEED. Technically they're accelerating, bumping into atoms, slowing down and accelerating again, but that's kind of like moving at a constant velocity.
– user113773
Apr 22, 2016 at 9:49