What is electricity? How does it work? Nikola Tesla's AC vs DC

this video is sponsored by the great courses plus imagine a world where with a device we can put in our vest pocket through television telephony we can see and hear each other as if we were face to face where motion pictures can be transmitted wirelessly where automobile carriages can perform operations involving judgment and where electricity is generated centrally and transmitted over vast distances to provide power to homes and factories that's the world we live in today and perhaps take for granted but there was a man who imagined these impossible technologies more than a hundred years ago and he along with thomas edison have arguably had more of an impact on the modern technologically advanced lifestyle we enjoy today than any other scientists past or present that man of course is nikola tesla yet this giant of imagination and innovation died nearly penniless and almost forgotten but there's no doubt that history has posthumously rewarded him with the accolades and recognition that he richly deserves perhaps tesla's biggest contribution to the world was his innovations in alternating current technology that allowed electrical power transmissions over long distances and the invention of the ac motor that allowed this ac power to be used by factories and businesses the adoption of this technology was an uphill battle because thomas edison's dc or direct current systems had been the standard early on edison tried desperately to convince the world to go with the dc and even stage an electrocution of a convicted criminal by ec current to show the public how dangerous ac technology was but ac eventually won out because the underlying truth about superiority of any technology lies in the science and science has an objective truth that is difficult to silence what does science have to say about edison's dc versus tesla's ac technology in order to explain this i'm going to explain how electricity works in general using a simpler analogy of electricity flowing through a wire that you might find more relatable and that is water through a garden hose that's coming up right now [Music] tesla was born in what is today croatia his father wanted him to be a priest but as a teenager nicola was fascinated by math and physics and instead became an engineer at 29 he immigrated to the united states with four cents in his pocket but he had a recommendation letter that got him a job redesigning direct current generators at one of edison's factories in new york city tesla only lasted about a year on this job partly because his ideas on alternating current technology conflicted with edison's dc what is ac and dc anyway and why is one superior to the other to understand this you have to understand some basics about electricity so what is electricity all materials are made of atoms atoms have a positively charged nucleus and negatively charged electrons surrounding the nucleus these electrons are bound to the nucleus due to their electromagnetic attraction to the oppositely charged nucleus but electrons in the outermost shell of the atom called the valence shell can sometimes become free due to external forces these electrons that escape from the valence shell are called free electrons and they can move from one atom to another this is what can cause a movement of charge and this flow of electric charge is what electricity is all about materials that allow many electrons to move freely are called conductors and materials that don't allow much free movement of electrons are called insulators so for example if you look at copper you'll notice that it has one electron in its outermost or valence shell this can quite readily become a free electron that's why copper is a great conductor if we force this electron to move we create electricity an electrical current is the flow of free electrons from one atom to another there are three concepts that you should understand if you want to understand electricity and these are current voltage and resistance all three are connected if you change one the others will change too the relationship between these three properties is described by ohm's law named after german physicist georg ohm voltage equals current times resistance these are not easy to visualize because you can't see them so we will use the analogy of electricity as water think of a water tank with a hose attached to the bottom current measured in amps is the rate at which charges flow it's analogous to the rate of flow of the water at the end of the hose voltage measured in volts is the force required to make the current flow it's analogous to the water pressure in the hose resistance is a material's tendency to resist the flow of charge think of the resistance as the diameter of the hose the smaller the hose the higher the resistance so if you have two tanks with the same amount of water but one has a smaller hose than the other or higher resistance it will have a lower flow given the same pressure similarly a circuit with higher resistance at constant voltage will have a lower current but if water flow from the tank is constant but the diameter is smaller then pressure will increase similarly if current is constant in a circuit then a higher resistance will result in higher voltage how does this water analogy relate to direct current and alternating current dc is similar to the normal flow of water through the hose that we're seeing here the water flows in one direction in this scenario current flows at a constant rate over time this was championed by thomas edison in the famous current wars that pit him against nikola tesla who championed ac ac is like the water flowing back and forth within the hose 50 or 60 times per second this is called the frequency and is designated as either 50 hertz or 60 hertz and depends on the electrical system of the country this is where the water analogy is not so great because water doesn't flow back and forth in a hose but alternating current does alternating current is easily created by industrial electric generators and is now the world's standard for transmission of electricity why did this technology win out over dc even though thomas edison one of the most famous and powerful men of the 19th century tried his best to disparage it the answer has to do with efficiency and power delivery power is like the volume or amount of water coming out of the hose the reason electricity is generated is to send power to homes and factories the mathematical formula for power equals the current times voltage the greater the current and the greater the voltage in the transmission lines the more power that is available to be delivered using the formula pcl's iv you can see that the same amount of power can be transmitted either at high current and low voltage or low current and high voltage but one is better than the other you see the power cables used to transmit electricity have a certain amount of resistance per meter of distance the longer this cable is the more resistance there is in the power line and any time you pass current through resistance you create heat given by joules equation for electric heat where heat is equal to current squared times the resistance heat is wasted energy because it essentially robs the grid of useful power that is not delivered to homes and businesses but is lost to the air so it's crucial to minimize this heat otherwise much of the power that you want to deliver is going to be wasted since i is p over v from our power equation if we substitute that back into the heat equation we see that heat equals power squared times resistance divided by voltage v squared you can see now that in order to reduce heat we want to maximize voltage v to deliver the same amount of power because for any given power and resistance the higher the voltage that we can create in the circuit the lower the heat loss we will have while transmitting electricity in modern electric power grids electricity is routinely transmitted for hundreds of kilometers at hundreds of thousands of volts but voltage cannot be this high when it arrives at your home because it would be very dangerous and could easily electrocute you so it has to be stepped down before it gets to your house this is done by a transformer which steps down the voltage from hundreds of thousands of volts to typically between 100 and 240 volts which is the voltage of electrical outlets in most homes around the world this stepping up and stepping down a voltage is where alternating current shines in comparison to direct current direct current cannot easily be transformed from low voltage to high voltage and vice versa but this is quite easy to do with alternating current and here's why when alternating current passes through a coil it produces a constantly changing magnetic flux for maxwell's equations that say that changing electric fields create magnetic fields if we put a loop a ring of iron through the coil it can concentrate the changing magnetic flux to within the ring now if we wind another coil around the other side of this ring we can create electricity and induce voltage in the new coil because again according to maxwell's equations a changing magnetic field creates a circulating electric field it so happens that the voltage we create in the second coil is proportional to the number of loops or turns we place around the iron ring using this method we can create voltage that is much higher in the second loop than the original voltage in the first loop this is very roughly how a transformer works and this method is used to step up the voltage for transmission over vast distances to minimize energy loss and we can use this same method to step down the voltage to a safer level before it's delivered to your home by simply making a smaller number of turns and the step down transformer but as you can see transformers like this require a time varying voltage to function and since direct current is constant and only alternating current is time varying transformers like these only work with ac electricity in edison and tesla's time there was no easy way to transform voltage with direct current and this is the primary reason tesla's ac won out over edison's dc in the early era of electrical transmission you might ask can devices work equally well with dc or ac current many devices like light bulbs only require that electrons move they don't care if the electrons flow through the wire or simply move back and forth so a light bulb for example can typically be used with either ac or dc electricity the fact that alternating current powers most of the modern industrial world has made tesla the winner of the current wars but as in most wars there are always two sides to the story was dc really a losing concept long term not really you have to remember that most high-tech appliances today that are powered by batteries like your laptop cell phone and ipad are all powered by direct current in addition in the late 20th century engineers figured out a way to transmit electricity using high voltage direct current or hvdc it turns out that hvdc is even more efficient than high voltage ac for transmitting electricity over extremely large distances of a thousand kilometers or more this is because smaller cheaper lines can be used to transmit the same amount of power using dc and there's less induction loss because no changing magnetic field exists with dc unlike ac but the cost of dc transformers is huge tens of millions of dollars versus only thousands of dollars for ac transformers so hvdc is only cost effective for very long transmission lines edison's place in history as an inventor and electrician is secure but in many ways tesla went even further he envisioned fluorescent lights technology for the radio and remote control but he was an eccentric because along with these genius ideas he also spoke about crazy things like splitting the earth in half and creating a death ray that could destroy thousands of airplanes at the same time scientists didn't know what to believe in his time and they were slow to praise him tesla did not get his dual claim until after his death but i don't think anyone disputes today that he was one of the most forward-thinking and dynamic visionaries that ever lived now if you'd like to learn more about inventions like teslas that change the world there's a superb course available at great courses plus today's sponsor called inventions that change the world it consists of 36 college-level lectures by award-winning educator professor w bernard carlson at the university of virginia i was inspired by one of his lectures called electric light and power where professor carlson takes us on a fascinating journey showing both the cooperation and conflict that edison and tesla had leading to the battle of the currents a great course is plus you can enjoy in-depth lectures by not only dr carlson but also some of the best educators in the world in my opinion there is no better online learning service than great courses plus and i can attest that i would be a member regardless of whether they sponsored me or not it's really easy to sign up right now because they're offering a special deal for arvind ash viewers if you use the link in the description the great courses plus dot com forward slash arvin right now you're going to get a free trial but be sure to use the special link and if you have a question leave it in the comments section because i try to answer all of them i will see you in the next video my [Music] friend [Music] you

Channel: Arvin Ash

Views: 467,029

Rating: 4.9132938 out of 5

Keywords: nikola tesla vs thomas edison, nikola tesla electricity, how does electricity work, ac vs dc, how is electricity distributed to our homes, alternating current vs direct current, why is alternating current better, why is alternating current preferred over direct current, electrical transformer, how is voltage stepped up, how do transformers work, nikola tesla, tesla vs edison, alternating current explained, voltage current and resistance, electricity water analogy, current wars

Id: ag6ltdwqfms

Length: 14min 28sec (868 seconds)

Published: Sat Sep 12 2020