How Electricity Works - for visual learners

sponsored by brilliant this is not electricity you can't see electricity you can only see its effects such as light heat motion magnetic fields very

expensive bills and electric arcs take this simple circuit with a battery a switch a lamp and a wire connecting them all together the battery is adding energy to the circuit and the lamp is removing this transforming it into light

and heat we can flip the switch to control this what's happening is tiny particles called electrons are moving through the wire from the battery's negative terminal through the lamp and into the positive terminal they actually

move a very small distance but I'll explain that in just a moment many of us were taught that electricity flows from the positive to the negative that's because long ago Benjamin Franklin theorized that electricity was an

invisible fluid he rubbed a glass rod with a cloth which then gave him a shock he believed the cloth was adding more of this fluid making it positive while the person touching it had less which made them negative so he assumed that

electricity flowed from positive to negative schools then taught this information many still do and we call this conventional current some years

later Joseph Thompson experimented with a cafod ray tube a device with two metal plates in a vacuum when powered a strange Ray appeared and it oddly

traveled from the negative to the positive side he observed that a magnetic field influenced the Rays Direction he also noticed that when passed between electrically charged plates it deflected in the electric

field between them towards the positive side as we know like charges repel and Opposites Attract so the be must be made of tiny particles with a negative charge

that moves from negative to the positive he called these particles an electron and we call this electron flow unfortunately Benjamin Franklin had guessed incorrectly the cloth was

removing electrons from the glass rod and they were moving from the person to the rod the common analogy is that the battery is like a pump providing the pressure to push the current through the circuit we measure this electrical

pressure in the unit of Volts for example this battery is rated to provide 1.5 volts and this one is rated for 9 volts the water flowing through the pipe is similar to the electrons flowing through the wires we measure the flow

rate in quantity per time and we measure the current in ampir or just amps 1 amp is equal to 1 K per second which means that if one amp was flowing through this

wire then we would have one Kon of charge per second passing this point an experiment by Robert milikin calculated the charge of an electron which is a

tiny number but from that we can calculate how many electrons are flowing and we see that 1 amp is equal to around 6.2 quinon electrons per second so we

just say 1 amp to make it easier the lamp is adding resistance to the Circuit similar to a section of thin pipe limiting how much water can flow we measure the resistance in the unit of ohms so the voltage is the pushing force

which moves the electrons and the resistance makes it difficult so it limits the amount of current which can flow but we can use ohms law to calculate the resistance voltage or current in a circuit as long as we know

two values so if we measure the current in this circuit and we know the voltage then we can easily calculate the resistance from that we can calculate how much energy is being consumed by the way I did make these handy mugs with all the

formulas on making it quick and easy to use links down below if you would like one so where are these electrons coming from well they are already in the wire although some do come from the battery the wire is typically made from copper

which is just a structure of many tiny copper atoms atoms are so small that this cubic centimeter of copper contains over 84 sextilion atoms so this wire

contains a lot more an atom is just a collection of three particles the electron Neutron and proton different elements have different numbers of these particles these elements are listed in the periodic table and here we can see

copper I'm going to use the bore model to illustrate the atom but some of you will be familiar with the more accurate quantum mechanics model of an atom this is very complex and Beyond this video so we're going to use the bore

model this shows that the carer atom has 29 protons and 35 neutrons at the center which forms the nucleus it also has 29 electrons around the nucleus in

different orbital shells in the outermost veent shell there is one electron which is free to move around to other copper atoms due to ambient thermal energy these electrons will naturally move around they are mobile

and they move randomly in any and all directions these mobile electrons are bouncing off of atoms and ending up roughly where they started well some move left some move right so the average is zero the electrons are negatively

charged and the protons are positively charged neutrons have no charge when an electron leaves the atom there are more protons so it has a positive charge and

we call this an ion the copper atoms are all sharing electrons so inside the wire we have the same number of electrons and protons therefore it is balanced and no

charge exists inside the wire the protons are positively charged and their electric field lines Point radially outwards while electrons are negatively charged and their field lines point radially inwards the field lines of two

electrons or two protons will repel each other but a proton and an electron will attract if we connect a plate to each terminal of a battery we would have a buildup of negative charge on one side and positive charge on the other side if

you imagine that these magnets are electrons and they are creating a neutral charge with their protons when the battery adds an electron it squeezes them so the charge has increased they only need to move a small amount for

that to happen we know that magnets can interact through their magnetic fields over a long distance without physical contact the same with electric charges their electric field lines Reach Out across the Gap we can see that by

applying a high voltage across these two plates the grasses will align with the electric field revealing the electric field lines by the way these arrows indicate the direction a positive charge would move in our case we use electrons

which are negatively charged so they move in the opposite way of the arrow which is a little confusing but just remember it moves from negative to positive our battery has a negatively and positively charged end so it has an

electric field by connecting a wire we can direct an electric field Through the Wire which helps to move the electrons from the negative to the positive terminal the electrons still move randomly but the electric field causes

them to drift towards the positive terminal as they move together Through the Wire they create a magnetic field around the wire we can see that using some compasses we use this to build electromagnets and it's also used to

drive electric motors so how far do electrons move well let's assume a current of 1 amp is flowing through this wire we can calculate the drift speed

Which is less than 0.1 mm/s which means it would take a very long time to travel this small distance but when I flip the switch the light turns on so how can I electrons travel

so slowly if you imagine these are electrons when we move an electron at one end its influence travels much further and faster in the wire we have an initial pulse of electric and magnetic fields propagating down the

wire that close to the speed of light then an electric field causes electrons to drift because of the surface charges and we'll see that in just a moment if I take 1 M of this resistive wire the resistance gradually increas increases

along the length of the Wire by the way this is different to standard copper wire we use it in things like toasters because the large resistance creates heat copper wires have almost no resistance if we apply 10 volts across

the ends the voltage gradually reduces along the wire but the current is the same at each point that's because the magnitude of the electric field inside the wires is the same so something is happening when we connect the wire to

the battery the battery contains a mixture of materials specifically selected because they produce a chemical reaction which absorbs electrons on one side and ejects electrons on the other side imagine that the chemical reaction

pulls in an electron and forces it to one end each time this happens the electric field grows and makes it harder for another electron to move across but

the chemical reaction force is so strong that it keeps moving the until the forces become equal and then it stops if an electron leaves the forces are

unbalanced so the chemical reaction forces another electron across to restore and maintain that balance for me to move these magnets towards each other

requires energy they want to repel for the chemical reaction to move this electron against the electric field also requires energy for every Kum of charge

moved it it requires 1.5 Jew of energy that is our voltage our electromotive Force this is the pressure the battery can provide other chemical reactions can

provide different voltages so due to the chemical reaction we therefore have a buildup of negatively charged electrons on one side and the other side has a shortage of electrons giving us effectively a positive and negative

terminal this charge at the ends of the battery is going to create its own electric field remember our piece of resistive wire has a neutral charge in sight because of the balance of protons and electrons no electric field exists

and so no current flows but when connected across a battery the battery pushes electrons into one end and pulls them out of the other so the buildup of charge at these terminals needs to transition from negative to positive

along the length of this resistive wire which forms a gradient of charge the charge is on the surface of the wire we can think of it like a ring there are regions with higher concentrations near the battery lower regions elsewhere and

a transition point where it flips from negative to positive imagine we took a disc of copper the protons and mobile electrons are balanced but if we added some electrons to the center they repel the other electrons away and they can

only go as far as the surface the charge at the center remains balanced so the excess charge must accumulate at the surface if we remove some electrons from the center the remaining electrons have more space and they expose some of the

positive charge of the protons this effectively gives us a positively charged ring so at the transition point we have a positive and negatively charged ring and on the sides we just have two rings which are both negative

or both positive but one is slightly less charged than the other whenever we have a difference in charge we have an electric field which points from the more positive to the negative so an electron in this field will be forced

towards the less negatively charged region if you imagine it takes energy to force these repelling charges together the energy is stored in the field between them we can use this to move other charges the gradient of charge

creates an electric field stor around the entire circuit which forces the electrons to move the energy is stored in a charge around the wires this resistive wire is the same diameter and the same material and the current is the

same at each point so the magnitude of the electric field must also be the same which is caused by the surface charges in a normal circuit the wires have almost no resistance and they are relatively thick compared to the thin

wire of the lamp the electrons are very easy to move through the copper wire but it's very hard to move them through the thin lamp filament so the surface charges mostly accumulate at the battery terminals and either side of the lamp

filament with very little gradient needed along the copper wire using a multimeter we can see nearly the full battery voltage across the lamp with only a small voltage drop along the wire if you think about water passing through

a hose when we place half thumb over the end we reduce the cross-sectional area so the water flows faster through this part even though the same quantity of

water flows before and after this point the same must happen with electrons in the filament of the lamp the electric field is stronger because of the steeper

surface charge gradient and that causes a higher drift velocity but the same quantity of electrons move so we have the same current we can look at the math behind that in my course where I have more time to explain this links down

below for that if you're interested but these electrons are going to collide with atoms in the filament and transfer their kinetic energy into the latice it's very difficult for the electrons to flow through so it keeps happening the

electrons slow down but the electric field keeps forcing them to move and they Collide again and again with each Collision the filament becomes hotter and hotter and eventually it becomes so hot that it emits visible light now the

circuit typically has a switch to control when current can flow through the lamp the battery is usually already inserted and the switch is on the positive side that means that this section becomes negatively charged and

this section becomes positively charged so we have an electric field around the wire but not in the wire so no current will flow when the switch closes some very complex interactions happen within a fraction of a second before the light

fully turns on I'm going to briefly explain what happens when the switch closes the charges along the face of the switch will meet and cancel out leaving just the surface charge rings with strong opposite charges this creates an

electric field which moves an electron as the electron approaches the positive ring that ring becomes slightly less positive and the negative ring become slightly less negative electrons are starting to move so a magnetic field is

developing and the change in surface charge creates an electric field the disturbance affects the immediate neighboring sections so the electric and magnetic fields travel like a wave down the wire in both directions but other

sections of the circuit are unaware of this change at this moment the electric field reaches out across the Gap and influences the surface charge charges elsewhere in the circuit creating small disturbance waves and a tiny current

here too as these waves move along the wire they will hit Parts which cause partial reflection waves these waves interact with other waves and they help to establish the gradient of surface charges in the electric fields which

stabilizes the circuit and the light eventually illuminates with a constant current flowing everywhere in the circuit all of this happens the moment we flip the switch the El Rons move such a small distance that they can't carry

the energy from the battery it's the electric field in The Wire that accelerates them to deliver the energy where needed and this electric field is due to the surface charges along the wire it can be difficult to understand

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