Basic Electricity & Magnetism Lecture Part 1.mp4

welcome to the presentation on principles of magnetism and electricity this presentation offers a very light introduction to the phenomena of magnetism and electricity the important takeaway from this presentation is the general ideas and concepts no math will be used in these slides but we will highlight the relationships that are easily shown in simple ratio and proportions the intent here is to give you a visual understanding of these phenomena history has to give somebody credit for everything so in this case Thales the famous Greek some 2,500 years ago notice that after he rubbed a piece of amber with a woolen cloth that the amber would attract lightweight items such as dust straw feathers and lint I'm guessing that he was probably polishing pieces of amber for the marketplace and he was using a woolen cloth this same principle can be discovered on a daily basis remember one time I was sitting in a restaurant and when I eat by myself I have nothing better to do than play with whatever's in front of me so I picked up the sleeve that my straw came in for my soft drink I held one end in in between my thumb and forefinger and then I took my other thumb and forefinger and slid it along the length of the sleeve to flatten it out I was going to fold it up or tie it in a night I can't remember now but after sliding my fingers across that sleeve when I brought my hand near it it was attracted to my hand that is static electricity our modern term electron is the Greek word for Amber so this is one of the many examples where the actual meaning of the word has no relationship to how it's used today quite a few years later a cat named Dufay actually in 1733 found that if he rubbed against a piece of glass the glass and his fur would become charged or electrified he also found that the charged glass would attract certain things that his fur would repel or push away from this experiment this cat decided that there were two elements of electricity and they were directly opposite although I'm sure that this is not the first instance of this discovery it was almost 800 years later that it was discovered that the same phenomena was observed when other two summer objects were rubbed together it was also noted that not all affected objects were attracted each other some repelled away when brought near and some were attracted when brought near this is the origin of the concept of different types of static electricity personally I never know whether or not to really believe this account or not however it's so widely accepted it probably was true but we've all heard the story in American history where Ben Franklin went out into a thunderstorm and flew a kite and he had a string tied towards the bottom of the kite with a key hanging on it and when lightning struck the kite the key lit up it glowed this is not impossible nonetheless we'll just take it at face value well Ben Franklin decided that the two elements of electricity should be named positive and negative now remember that he's supposing this from observable phenomena he cannot actually see what's going on so he surmised that there was something named positive and something named negative positive meaning and excess negative meaning a deficiency and these are the commonly referred to as plus and minus or shown graphically as plus and minus symbols and he surmised that there was a flow from an excess to a deficiency and since positive is excess and negatives deficiency he determined that this flow was from positive to negative this was and is referred to as conventional current flow from positive to negative however much later when electron flow was discovered it was discovered that the actual excess is an excess of electrons and in the mean time they had designated an electron is negative and a an atom missing electron as a positive ion so the two were in conflict so conventional current flow is called conventional because it goes back to Ben Franklin and electricity flowing from positive to negative whereas in reality electron flow the actual flow from excess to deficiency is from minus to plus and some some schools too conventional current flow from plus to minus other schools teach electron flow from negative to positive it really doesn't matter because you can't see the actual movement anyway so it's it's basically terminology to describe to observe behavior but not actually observed physical motion of something I'm sure everyone listening to this presentation can provide multiple accounts of personal discovery of static electricity some of it benign some of it humorous and some of it may be even painful I remember I was walking through Disney World inside a building and I noticed that there was a lot of static electricity the atmosphere was just right and you know dryness and what-have-you and every time I got my finger there anything metallic a big arc would jump off the end of my finger so I was walking along with a friend and his brother and I scuffed my feet really good got a good charge going I reached around behind my friend it put my finger up be behind my his brother's ear just close enough to get a big arc it it sounded like a snap like breaking plastic and boy did he jump now you probably think that's mean but anyway not bad as Reuben here because eventually that static charge is going to dissipate and down those babies are going to come this list is called the tribal electric series if you read down through this list human hands usually too moist though are very positive down towards the middle steel which is neutral and down towards the bottom Teflon which is very negative so through the years of experimentation this list was put together in the order verified so some objects when rubbed together display a very strong force while others very weak as objects of different composition were experimented with this list evolved today this list is as you see it here on the screen the materials at the top and red text have been determined to give up electrons to the materials lower in the list yes that means that when you rub glass and fur together you get a static charge even though they are both in the upper half of the list another example would be silk and cotton they're both in the upper half of the list if you rub silk and cotton together and ladies have probably discovered this more than men wearing a cotton undergarment than a silk blouse but this combination is available for the guys too and maybe you were undressing in the dark and as you were pulling off your silk blouse you felt some static discharges and maybe even saw the sparks many of us have been known to do this in the dark just to see the sparks now if you take silk and rub it against glass the silk is now negative compared to the glass so it's the relationship of +2 - is determined by where they're at on this list the higher on the list the more positive the lower on the list less positive so in the first case of silk and cotton cotton rubbed against the silk stripped electrons off of the silk leaving some of the atoms in the silk missing electrons and therefore positive whereas when silk is rubbed against glass the silk actually rubs electrons off of the glass and the silk is now negatively charged with an excess of electrons leaving the glass missing some of the electrons from the outer orbits of its atoms so it is proper to say that the silk is more positive than the cotton and yet less positive than the glass so the most positive is positive and the least positive is therefore negative the same rules apply throughout the list top to bottom so at this point you should be realizing that electricity is the separation of charges an atom electrically neutral has an equal number of positive elements and negative elements but if you remove one of the negative elements then you have more positive elements than negative elements left behind therefore you have a net balance of positive and whatever device took the electron away it now has an extra electron therefore it's negative so producing an electrical charge by creating friction between two dissimilar materials off of this list was the first method discovered to produce electricity and everything else followed as people became more familiar with the phenomena now remember this this was discovered we'll say by Thales the ancient Greek and then he showed it to friends eventually this gets around people play with an experiment and then they draw conclusions so a lot of what is known about modern electricity is still based on those basic conclusions this older gentleman here Dmitri Ivanovich Mendeleev is basically credited for the periodic table and we give a date here of 1869 this is just to give you a chronological reference and the idea of the periodic table you ball because it was discovered that not all atoms are alike everything is made of molecules and molecules are made up of atoms but not all atoms are alike for instance h2o water two atoms of hydrogen and one of oxygen oxygen as a heavier material has more components in its nucleus and more electrons orbiting the nucleus so not all atoms are alike this periodic table really is the work of more than just this gentleman there were hundreds of scientists that really contributed to this periodic table and the reason they call that a periodic table is because they have arranged them to show the periodic similarity asthma you go through from the lightest which is helium I'm the hydrogen the lightest which is hydrogen to the heaviest which is down in the lower right-hand corner so it goes from the upper left-hand corner across to the lower right-hand corner and so the they pick this number of columns because as you go through the elements from the lightest of the heaviest periodically one of them displays similar characteristics to one of them earlier in the list so if you look at hydrogen it's yellow and then right underneath you have a column of green than blue then you have a number of columns of orange then you have red yellow cyan and back to blue of interest to us because we're you know talking about basic electricity our copper silver and gold CU AG and au copper is the lightest of the three silver is medium weight and gold of course is the heaviest everybody knows Gold's heavy what is summer about these three is that each of them in their outer electron orbit called the valence ring have only one electron in that outer orbit and it's loosely attached to the atom which means it's easily stripped off for the movement of electrons hence they're called conductors another vertical column here would be silicon mium in selenium these are three elements used to make semiconductors and of course silicon now is the most domino's so the periodic table here is more than just a list of elements conductors and insulators are extremely important to our understanding of basic electricity if you want to control the movement caused by applying an electro-motive force you need to have influences that oppose it going where you don't want it to go and you have to provide a path for it to go where you want it to go it's something like digging a ditch to drain a pond that you dig the ditch to get the water to go where you want it to go so the size of the ditch would be an insulator and the depth and altitude of the bottom of the ditch would be the conductor so to speak so a brief examination of the apparent structure of atoms will assist in your understanding of both insulators and conductors atoms are proposed to be made up of a nucleus around which electrons travel in orbits of defined distance in each level of orbit contains a definitive quantity of electrons the outermost orbit level is referred to as the bigness level or valence ring if the particular element such as copper the one that we're most interested in as a conductor happens to have only one electron in its outer orbit it is classified as a conductor as the quantity of electrons and the outer orbit increases they are more tightly bound to the nucleus so an element like silicon which has four electrons in its outer orbit is classified as a semi conductor or an insulator in copper which has only one electron in the outer orbit is classified as a conductor because that lone electron is not tightly bound to the nucleus so we'll look a little deeper at the conductive properties niels bohr introduced this model of an atom back in the early 1900s and I want to say at this point and I will probably repeat myself a couple more times no human being has ever seen an atom that is to say no human being has ever had the image of an atom focused on the his retina whether it be from a lens microscope the reason that they say they can see atoms with an electron microscope is basically they throw energy at an element and then they look at the reaction and determine what they're looking at from the reaction is kind of like reaching your hand into a dark hole where you can't see anything and then moving your hand around in there to see what happens you and you can feel with your hand you say okay this feels like this this feels like that therefore what's in there must be a dog because when I pet it it I can feel it wiggling so it must be wagging its tail so if you've never seen a dog before now you really have a hard time reaching in a dark hole feeling something warm and furry and petting it and saying it was a dog so remember no human being has ever seen an atom before so this model that you're looking at here the Bohr model represents a nucleus which is to represent the bulk of the mass and a nucleus is made up of protons and neutrons orbiting around the nucleus are a number of electrons equal to the number of protons in the nucleus a proton is positive you see the nucleus error plus 29 and then there should be 29 negative electrons and those electrons have energy and if they didn't had no energy at all then the electrons would collapse into the nucleus and the two charges the two electrostatic charges would come completely together then cancel the field so the electrons actually have energy and they're trying to move away from the nucleus but the positive charge in the nucleus is holding the electrons from going out any further than what is shown here this is a little bit different model of an atom but it's still it's still a Bohr model just has a little dimension to it this is a newer graphic showing the Bohr model and the valence electron is emphasized as a light green ring so that is the Venus electron or the electron that can easily be freed up if you apply a force now that force doesn't have to be magnetic or electrostatic it can be thermal if you heat up this atom the electron has become more agitated and this free electron will fly completely out of its orbit and then drop back in so they call that thermal emission so almost all objects have some thermal activity even at room temperature at some point we've all played with magnets whether it was the magnets on the refrigerator or we paid particular attention to them in science class or magnetic things that we come across in our daily lives and we stop and play with them for a minute well what is magnetism at the heart of magnetism is the electron the electron is presumed to have a magnetic polarity just like the earth and the electron has a spin like the Earth spins as it orbits around the earth electrons spin as they orbit around the nucleus if you've played with enough magnets you know that depending on how you hold them against each other in one direction they attract and hold tight together in the other direction they repel so every atom has electrons every electron has a magnetic field as seen here and by the way they show the magnetic field as lines the lines are only to depict that there is a magnetic field there and if it's comparative then between one object and another the denser the lines the stronger the magnetic field but theoretically these lines of force or flux as they call it magnetic field actually extends out indefinitely so if you took two of these electrons and they were facing opposite directions in other words their spins were in the opposite direction as you see here the spin of the electron determines the polarity and if you look at those magnetic lines of force and look at the direction of the arrows you'll see that the lines leaving the North Pole on the one on the right are traveling in the same direction as those going into the South Pole on the electron on the left so these two magnetic fields cancel each other out completely so although every electron has a magnetic field in almost all atoms the net magnetic field is zero because the electrons balance each other out however in one material in particular that's iron and we refer to this ferromagnetic material the way the electrons are orbiting around the nucleus they don't all cancel out so every atom of a ferromagnetic material has a net magnetic field remember all other materials have zero magnetic field because their individual magnetic fields equal and they're flipped in opposite directions they cancel only in ferromagnetic material do all of the atoms have a net magnetic field however if you take two ferromagnetic atoms and place them next to each other in opposite directions then they two cancel each other out so iron or ferromagnetic material like steel a nail screwdriver blade etc they are ferromagnetic material but because their atoms which make up their molecules are arranged in random directions you get a net balance of zero for the magnetic field so if you've ever member made a magnet meaning you've actually magnetized a piece of iron or steel this is how you probably did it you ramped some electrical conductor around a nail or a screwdriver blade and then you touch the two ends of the wire to a battery and as current flows through that conductor the electrons flowing through the conductor since they're all going in the same direction their magnetic field joins together to make a very intense magnetic field inside of that coil and inside of that coil was that nail or that screwdriver blade that forces the the molecules in the ferromagnetic material called domains or dipoles meaning two poles it forces them all to line up in the same direction and then when you remove the magnetic field created by the wire wrapped around it not all of them go back into random order so it's left with a net magnetic field and now you have a permanent magnet now in manufacturing when they make a permanent magnet they take ferromagnetic material in a semi molten state in other words it's not quite liquid yet it's still a solid but it's very very malleable you know it's red-hot and just below the temperature for making it you know melting to a liquid they place it inside of a really strong electromagnetic field you know created by electricity flowing through a coil and they by a conveyor it goes into that field and the magnetic force from the coil with the electricity running through it forces all of these domains the ferromagnetic material molecules it forces them all to line up with all their north poles in one direction South Poles and the opposite at that point it is a very powerful magnet and then while it's still hot and being magnetized they quench it with water and so as the metal hardens again all of the domains or dipoles are all lined up in the same direction and now you have a really powerful permanent magnet so when you go back to this picture you can see that the source of magnetism is the electron even though we think of a magnet as a bar magnet with the north and a South Pole it's actually comes from the electrons that have not completely randomly balanced each other out to a NetZero magnetic field but instead they're they have a net magnetic field this is a no-brainer opposite forces attract like forces repel and this is evident in nature as well as in physics physics is actually kind of a contraction for physical philosophy so physics the study of physics the science of physics is physical philosophy philosophy so opposite forces attract like north and south poles like forces repel and this goes for positive and negative positive repels positive positive attracts negative ok here's two charges and we're just going to further emphasize what we've been saying notice that the lines of force emanating out from these charges one negative one positive are traveling in opposite directions so if you place two like forces next to each other as seen here on the left they're lines of force or they're flux joins together and draws the two objects closer and closer together so the lines of force are always seeking to be as short as possible so in this case this negative and positive charge would come together and then the magnetic field would cancel out the force is still there but it's cancelled out because it is trapped between the two now put this in your mind for pondering let's say that you took this positive force in this negative force or this positively charged object and negatively charged object they're also called ions and you put them near each other but you did not allow any means for them to come closer together in other words let's say you put an insulator between the two then they would hold the state that you see right here and there would be a strong electrostatic field between these two charges but they're kept from coming together and cancelling by the insulator that's placed between them over on the right side you see two positive charges there lines of flux or force lines because they're traveling in the same direction cannot connect and join together so when you try to push two like forces together the fields aren't compatible and they can't cross each other so in other words you are actually compressing the field from these two objects as you try to force them together if you have ever taken two really strong permanent magnets and put one on each hand and held them close to your body so you could steady your hands in other words like on your stomach or chest and then slide them towards each other at some point you start feeling the resistance and if you watch if it's a really strong permanent magnet you will not be able to push them all the way together what usually happens is the force becomes the force of repulsion becomes so strong pushing back against the muscles in your arms that it actually is greater and then your hands slip and it go they go by each other because the member the north and south poles are attracting the same as the two north poles are repelling etc okay we've talked about atoms and electrons this is a copper atom at least it's a graphical representation of a copper atom I did not draw this diagram I pulled this off the web and you see there's 29 electrons orbiting at different levels around the nucleus the outermost one is the one that we are most excited about no pun intended that is the valence electron or the free electron so if we look at a copper conductor which is made up of millions of these atoms these copper atoms and each copper atom has a free elect crime so we have a very thin density here of copper atoms but it'll do for our illustration now those electrons that have the stars on them that's the free electron they are loosely attached to the nucleus so any energy imposed on this system will cause them to leave their orbit and then pop back in so if we were to heat up this copper wire all of these free electrons the ones with stars on them would pick up the energy of the heat waves going into the conductor and they would fly off by something called thermal emission then they would pop back in now electrons are all the same so it doesn't matter which atom and electron pops back in - you'll see in the next slide that we're going to take and apply a negative and a positive charge now remember the electrons are negative that's the little dots with the stars and the nucleus azar have a net positive charge if you have 29 electrons and 29 protons so you have 29 positive charges in 29 electrons of equal negative charge it is electrically neutral so these atoms are electrically neutral however if you apply a charge across this conductor minus the positive that - over there represents excess electrons in other words their electrons that have been stripped off of atoms in place in containment the positive is a bunch of atoms that are missing electrons so on the left end of this copper conductor you have a negative charge and negative ion a negative force which is attracting the protons and all of these copper atoms well the coppers are solid those nucleuses are not going to move this negative charge on the left side is so repelling all the electrons in this conductor over towards the right over on the right you have a positive charge that's repelling all the nucleuses back towards the left but again it's a solid they're not going to move that positive charge over there is also attracting all of those free electrons so on the left side you have an excess of electrons which are repelling all of those free electrons towards the right and over on the right you have a positive charge that's pulling them that way so I couldn't do it in this graphic but basically those valence electrons the ones with the stars on them are basically popping in and out all the time they're very loosely coupled and is they become warmer you know the copper wire warms up they pop in worn out so when we look at this graphic here we have a bunch of free electrons that are randomly popping in and out and if we apply it charge to them the negative pushes them over to the right and the positive pulls them to the right I want to mention that this graphic of the electrons moving through a conductor was not created by me I added the minus and the plus charges I got it somewhere off of the internet but I want to give credit now this is for educational purposes so it's okay but you understand these free electrons wants or they come once they come under the influence of an external minus and positive electrostatic field remember there are lines of force going from that negative charge over to that positive charge and in the middle or all these loosely coupled a couple of electrons they now take off going towards the positive so that minus and plus could be a battery now if you put a wire across the two terminals of the battery that was going to get really hot because you're shorting out the battery and there's too much current flow for that conductor speaking of batteries we briefly we briefly glanced at how we could displace electrons with friction and create a static Church one thing I forgot to mention in the previous graphic several those graphics where we were looking at a negative and a positive ion in the lines of force between them the charge the electrostatic field between them the strength of that force that's pulling the negative and the positive charge together is called the voltage is measured in bolts and it's a specific amount of force the closer the two charges get together the stronger the pull and the higher the voltage as you move the charges further apart the field weak weakens because it has to emanate over a much larger volume and so you have a weaker field and therefore a lower voltage so voltage is how we measure electro-motive force it's an electoral force that wants to motivate things to move electro-motive force the invention of the cell the lead-acid cell which separates electrons from atoms with a chemical reaction was the first great invention to provide a constant source of electro-motive force EMF or voltage by the way this is a cell and not a battery the battery is two or more together such as this this is a battery of cells you might also use the term battery when referring to in artillery battery one artillery unit is a cannon a group of them is a battery artillery battery so now we call cells batteries and vice versa so everybody seems to know what they're talking about or referring to and they say a battery but remember a battery is actually a group of cells so a 9-volt battery is really a 9-volt battery made up of half a dozen individual cells inside whereas a triple-a double-a be size C size D size those are literally cells they're not batteries now this particular battery of cells is what was used to power Telegraph stations so this is what power the telegraph system now the way a battery works or I should say a cell there's a chemical process that eats away at one side of the cell and transfers negative ions over to the other side leaving the side that it ate away from positive now remember I told you that there's a force between the positive and the negative charges that's trying to pull them back together so the chemical force pull them apart and in the beginning when it first starts doing that it's very rapid but remember this as it keeps pulling negative charges away and leaving it positive the field strength between those two poles on the battery starts increasing in other words the voltage becomes greater and greater until at some point the pressure or the force to pull the negatives back to the positives equals that of the acid that's pulling them apart and then it stops charging at that point it is an equilibrium and that's the highest voltage that that cell can attain okay here we have a loop of copper wire represented by the reddish circle with the blue inside of it so this is a loop of copper wire suspended in space and then we have magnetic flux or lines of force that are traveling from the bottom of the image towards the top now remember the influence that these electrons have on each other that positive repels well negative repels negative positive repels positive negative attracts positive and so forth so remember each electron is a little magnet of its own so if we take an external magnetic field and apply it to that copper conductor those electrons are going to feel that however the electrons are in the loop of wire are only going to move when the magnetic field is moving so we can either we can move the loop of conductor back and forth through the magnetic field to get the electrons in the loop of copper to move or we can move the magnetic field in and out of the loop so I'm going to run this little a video clip here I did not create this I got this off the web and what you'll see you have two graphs there if you look in the lower left hand corner a blue and a green the blue is going to be movement of the magnetic field now remember that you could take and hold the copper loop stationary and then take a magnet like a bar magnet in your hand and move it in and out of the copper loop or closer to it and further away and that's one way to get a result or you can hold the magnet still stationary and then move the copper conductor back and forth in the magnetic field but when you have a magnetic field remember that magnetic field is produced by electrons who have all aligned their magnetic polarity to make one big magnetic field when you impose that on a copper conductor that has free electrons the electrons in that copper loop we're going to come under its influence but only when something is moving so if you move the copper wire through the field then as you move through the field the field is going to displace those electrons and make them move if you reverse the direction then the electrons are going to go in the other direction or instead of moving the magnetic field move the conductor and when either way something's moving or you can move them both at the same time normally you just move one so think about this if this were in outer space you wouldn't know which was moving you would just see that there's motion between the two so let's run this little graphic and first the magnetic field is going to become more dense and as it goes in it induces a current notice that magnetic field comes out from the conductor because the electrons are now lined up and moving or you can rotate it notice the magnetic field that results from the electrons moving in the copper wire it's interesting to point out that when you use a magnetic field in motion to get electrons to move in the conductor that electron flow produces now a magnetic field that opposes the one that produced it is called counter EMF C EMF this takes a little bit of pondering but the important thing to remember is if you have a conductor and you have a magnetic field and you place them in proximity if you move one is going to affect the other so you're going to get movement of electrons in that copper wire whether you move the copper wire in and out of the field or move the through the field back and forth across the copper wire that is electromagnetic induction you're inducing current flow in that conductor because you're passing magnetic lines of force through that conductor which influences those free electrons to move and they're all going to move in the same direction because that's based on polarity so as you slide the magnetic field through the copper wire the electrons all go one direction and when you bring it back they reverse and I'll go the other direction that would be alternating current okay you're continually alternating the direction that the magnetic field is moving through the conductor therefore the movement of the electrons in the conductor alternate back and forth what we have here is a coil of conductor which is a partial spool of red 18 gauge conductor right on the support came on I just pulled the ends off and hooked it up to the arsenal' vol meter movement what you can do is watch this needle they can see just getting the magnet near this coil of wire you can see some movement of the needle I'm going to slide it inside you can see that you can almost get the meter to peg notice that if I pull it this direction the current goes one way if I push it in it goes the other is if I pull it back and forth I can keep the current flowing but it's alternating the direction it goes first one direction then the other direction now remember that there's a spring on this needle so it tends to bounce so let's settle down okay now so what we have here this is a very strong permanent magnet okay and that's why I have a tape to the stick because they're just very powerful and it's hard to remove them from ferromagnetic material once they attach and the stick helps now remember that inside of this permanent magnet are molecules called domains or dipoles and each of these molecules have a north of South Pole in most ferromagnetic material they are randomly oriented and they cancel each other in this particular material this was manufactured as a permanent magnet so they forced all the domains to be all lined up in one direction and then solidified the material and that forms a permanent magnet but the magnetic field from this magnet comes from the electrons in the magnet remember electrons repel electrons so this copper wire here you're looking at the red plastic insulate insulation but inside the insulation is copper wire and that copper is made up of the copper atoms that we've shown earlier in this presentation so when I move this magnet in here the electrons in the magnet the magnetic field from the electrons and the magnet repel the electrons of the copper wire now another phenomenon want you to notice I'm going to hold this as stationary as I possibly can and I'm going to disturb the magnetic field with a screwdriver but see how hard that is to get off of there some of them hold us down a little bit better and watch the needle can you see the needle moving the needle is moving because when I bring this ferromagnetic material in here it is intensifying the magnetic field because the magnetic field moves with less resistance through ferromagnetic material than does through air that causes the magnetic field to move so this is how a proximity sensor works a proximity sensor actually has a electromagnet not a permanent magnet and it has a coil of conductor and this is stationary and when a metal object moves by see the needle moving but an object moves by it disturbs the magnetic field and the current flowing in the sensor amplifier which would be this device now senses that change in the magnetic field and says AHA there's an object there another thing to point out is that if I slide the magnet in and out you see that I can maintain current flow but I can also move the coil of conductor I don't have to move the magnet I can move them both and get a lot so something has to be moving if you move the magnet the electrons in the magnet moves the electrons of the wire if you move the wire then the electrons in the conductor moving against the field created by the electrons in the magnet caused current flow so it doesn't matter which one you move move the coil who the magnets or move both another thing I want to show you is you see when you have a big loop of wire you get a lot of heavy action but if I just pass it by a single conductor in other words if I separate out one conductor here you see that the needle motion because the magnet only has influence over the electrons in this small area to the conductor you only get a little bit of induced current but when you do it inside the coil you the magnet the permanent magnet is influencing all the electrons on this full length of this wire because it's wrapped up in a coil as opposed to getting just a tiny little deflection on the meter for this motion in our previous demonstration we demonstrated electron flow or current flow by either moving a coil of conductor through a magnetic field are moving the magnetic field through the coil of conductor in the diagram here we have a single loop of conductor and in that conductor the electrons are traveling around in one direction which means that all of their magnetic fields join together to form one magnetic field that surrounds that loop in this little animation which I did not create I got it off of the web we see what happens when you have many loops of conductor and you have current flowing through it the individual magnetic fields of the individual loops all join together to make one intense magnetic field and the magnetic field inside the coil is very intense this form is called a solenoid and that intense magnetic field inside of the solenoid is used to attract ferromagnetic material like a ride against a spring to pull it into the center of the coil and then when you turn the coil off spring pulls it back out so energizing the coil pulls the rod end the energized the spring pulls it back out that's solenoid motion okay here's another animation that I did not create I got it off the web and if anybody sees their material on here and they want credit you just email me and I'll put some credits at the beginning or the end now here what we have and I'm going to pause this a minute notice that we have a rotating loop of conductor and at the end of the loops outside the magnetic field there are we'll call them if you like split rings are called commutator segments so the upper end of the loop is connected to the blue piece of metal curved metal and the bottom of this loop of conductor is attached to the red so as the loop of conductor rotates inside of the magnetic field those commutator segments rotate with it attached or I should say in electrical contact with the commutator segments our brushes those are the two little dark grey rectangles that then have copper wires leaving them and going over to the battery so here's the idea with that battery in place you're going to have current flow you see positive on one of the battery of the other end electrons are going to flow through the copper wire up to the top through the brush into the blue commutator segment out through the top half of that loop down the other end and then back across the bottom of the loop to the red segment out of the brush on the bottom through the copper wire and order the positive end of the battery as the current flows through that loop those electrons flowing through that loop all of their magnetic fields add together that magnetic field opposes the magnetic field of the horseshoe magnet and something's got to move since the horseshoe magnet can't move then the loop so really you could say that the electrons flowing through the loop create a magnetic field on the loop and the horseshoe magnet since it's stationary that forces the magnetic field on the loop the rotating loop to move so let's continue the sign and you see that in order to keep this thing moving you have to keep reversing the polarity through the loop because once the loop repelled around in one direction it would be attracted and then line up and stop so just as soon as the loop gets in the position to where the North Pole has reached the North Pole on the loop has reached the North I'm sorry the the North Pole on the loop has reached the South Pole on the horseshoe magnet it would attract and stop right there right at that instant the commutator segments are in a position where we reverse the current flow and now we've reversed the magnetic polarity of the loop and so what was attracting is now repellent and it just keeps going around in a rotary motion okay this looks like the exact same device actually the whoever created this animation rotated the horseshoe magnet around perpendicular and it really doesn't matter because the magnetic field is still passing through the loop and then they've attached something to external to mechanically make the loop move through the magnetic field of the horseshoe magnet remember the previous animation you had a battery that pushed electricity through the loop and then the magnetic field of the loop working with the magnetic field of the horseshoe magnet a forced motion of that loop so the magnetic field produced by the loop fighting against the magnetic field of the horseshoe magnet gave you your motion in this case we're going to do just the opposite we're going to take and a external mechanical means in this case say a windmill and we're going to rotate that loop and as that loop rotates around through the magnetic field the magnetic field of the horseshoe magnet is going to force electrons to move in the loop and the electrons will flow you know in one in one case they'll flow out through the blue commutator segment up to the brush down and over through that light bulb and then back to the bottom into the red commutator segment and back into the loop so we have a permanent magnet with a stationary magnetic field we have a single loop of wire or conductor that is rotated by wind energy we have the loop is extended outside of the rotation by commutator segments now if you think about this the loop that we're inducing current flow into continues through this segments through the brush through the wire through the light bulb through the wire through a brush back into the other commutator segment back to the rotating loop so this is really one loop of conductor that includes the commutator segments the brushes and the little light bulb so when we rotate this a little bit later in this animation you'll see the light bulb will blink as the current is being induced into the conductor and then of course we'll have rotating in contact with stationary brushes so the commutator segments are being rotated in contact with the brushes and the brushes maintain the electrical connection and then we have a complete circuit through the filament of the light bulb or the filament of the light bulb is a conductor so we'll take and rotate the magnet around we'll get rid of the battery and we'll replace it with a light bulb which is a load and then the air will force the coil to move that induces current flow you can barely see the ball illuminating but it is illuminating ok this presentation is taking a little longer than I thought so I'm going to provide an intermission and we'll just call this part one so this is the end of part one of principles of magnetism and electricity and let me remind everyone who is watching this presentation that some of the graphics some of the images that I used I got off of the web in a case where all the material is not mine I do not monetize or in any way make any money off of this presentation and if you want mention of your material just email me and I will add it to the credits right now there's no credits again thank you for watching this and be sure to look for part two which I will begin working on immediately thank you

Channel: plcprofessor

Views: 110,928

Rating: 4.8414636 out of 5

Keywords: Basic, Electricity, Magnetism, PLC, Controls, Engineering, Engineer, Lecture, 01, Introduction, to, Relays, Programmable Logic Controller, training, tutorial, hands on, programming, learn, Learning, Lesson, AB, Allen, Bradley, Rockwell, Automation, free, download, courses, course, ladder, ladder logic, Micrologix, SLC, 500, inputs, outputs, troubleshooting, basic

Id: ctXdPP38Syg

Length: 60min 7sec (3607 seconds)

Published: Wed Oct 31 2012