This video was sponsored by Casta by Lutron. Imagine you have a monstrous route consisting of a artillery, a switching, a light bulb, and two wires who the hell is each 300,000 kilometers long. That is the distance light passes in one second. So, they would reach out half way to the moon and then come back to be connected to the light bulb, which is one meter away. Now, the question is, after I close this switch, how long would it take for the bulb to light up.
Is it half a second, one second, two seconds, 1/ c seconds, or none of the above. You have to move some streamlining premises about this route, like the wires have to have no resistance, otherwise this wouldn’t work and the light bulb has to turn on immediately when current guides through it. But I want you to commit to an answer and articulated it down in specific comments so you can’t say, oh yeah I knew that was the answer, when I tell you the answer later on.
This question actually relates to how electrical energy get from a power plant to your dwelling. Unlike a battery, the electricity in the grid comes in the form of alternating current, or AC, which conveys electrons in the power lines are just wiggling back and forth.
They never actually go anywhere. So, if the charges don’t come from the power plant to your home, how does the electrical energy actually reach you? When I used to school this subject, I would say that power lines are like this flexible plastic tubing and the electrons inside are like this chain. So, what a power plant does, is it propagandizes and pulls the electrons back and forth 60 experiences a second. Now, at your home, you can plug in a invention, like a toaster, which is mainly conveys accepting the electrons to run through it.
So when the power station propagandizes and plucks the electrons, well, they encounter resistance in the toaster element, and they dispel their vitality as hot, and so you can toast your bread.
Now, this is a great story, I think it’s easy to envisage, and I review my students understood it. The only problem is, it’s wrong. For one thing, there is no perpetual conducting wire that runs all the way from a power station to your house. No, there was still physical cracks, there are smashes in the line, like in transformers where one coil of cable is wrap on one side, a different coil of cable is wrapped on the other side.
So, electrons cannot perhaps spurt from one the other. Plus, if it’s the electrons that are carrying the energy from the power station to your machine, then when those same electrons flow back to the power station, why are they not likewise carrying vigor back from your house to the power station? If the flow of current is two ways, then why does vigour simply flow in one direction? These are the lies you were coached about electricity, that electrons themselves have possible force, that they are propagandized or pulled through a ceaseless conducting loop and that they fade their force in the device.
My claim in this video is that all of that is false.
So, how does it actually wield? In the 1860′ s and 70′ s, there was a huge breakthrough in our understanding of the universe when Scottish physicist, James Clerk Maxwell, realized that light is made up of oscillating electric and magnetic fields. The provinces are oscillating vertical to each other and they are in phase, intending when one is at its maximum, so is the other wave.
Now, he works out the equations that govern the behavior of electric and magnetic fields and hence, these motions, those are now called Maxwell’s equations. But in 1883, one of Maxwell’s onetime students, John Henry Poynting, is thinking about conversation of energy.
If energy is conserved locally in every tiny bit of opening, well, then you should be able to trace the track that exertion flows from one sit to another. So, “ve been thinking about” the exertion that comes to us from the sunlight, during those eight times when the flame is traveling, the force is stored and being transmitted in the electric and magnetic fields of the light.
Now, Poynting works out an equation to describe energy flux, that is, how much electromagnetic power is passing through an place per second. This is known as the Poynting vector and it’s given the symbol S. And the formula is really pretty simple, it’s just a constant one over mu naught, which is the permeability of free space eras E X B.
Now, E X B, is the cross product of the electric and magnetic fields. Now, the cross product is just a particular way of multiplying two vectors together, where you multiply their perpendicular proportions and to find the direction, you put your paws in the direction of the first vector, which in this case is the electric arena, and bend them in the direction of the second vector, the magnetic fields, then your thumb items in the direction of the resulting vector, the exertion flux.
So, what this shows us about light-colored is that the vigour is spurting vertical to both the electronic an the magnetic fields. And it’s in these directions as the light is traveling, so this makes a lot of smell. Light carries force from its root out to its destination.
But the kicker is this, Poynting’s equation doesn’t time work for light, it drives anytime there are electric and magnetic fields co-occur. Anytime you have electric and magnetic fields together, there is a flow of energy and you can calculate using Poynting’s vector. To represent this, let’s consider a simple circuit with a battery and a light bulb. The artillery by itself has an electric field but since no charges are moving, there is no magnetic field so the battery doesn’t lose energy.
When the artillery is connected into the circuit, its electric discipline provides through the route at the speed of light.
This electrical plain moves electrons around so they increase on some of the surfaces of the conductors offsetting them negatively charged, and are expended abroad leaving their faces positively charged. These face accuses create a small electrical discipline inside the wires, starting electrons to wander preferentially in one direction. Note that this drift velocity is extremely slow around a one-tenth of a millimeter per second. But this is current, well, conventional current is defined to flow opposite the gesture of electrons, but this is what’s constituting it happen. The commission on the surfaces of the conductors also appoints an eclectic battlefield outside the wires and the current inside the wires establishes a magnetic field outside the wires.
So , now there is a combination of electric and magnetic fields in this space in various regions of the circuit. So, according to Poynting’s theory, vitality should be flowing and we can work out the direction of this intensity move expending the right hand rule.
Around the battery for example, the electric field is down and the magnetic field is into the screen. So, you find the vigour flow is to the right away from the battery. In fact, all around the battery, you’ll find the exertion is radially outwards.
Energy is going out through the sides of the battery into the fields. Along the cables, again, you can use the right hand rule to find the force is flowing to the right. This is true for the fields along the top cable and the bottom wire. But at the filament, the Poynting vector is directed in toward the light bulb. So, the light bulb is getting energy from the field.
If you do the cross product, you find the energy is coming in from all around the bulb. It takes numerous tracks from the battery to the bulb, but in all cases, the energy is transmitted by the electric and magnetic fields. – People seem to think that you’re pumping electrons and that you’re buying electrons or something, which is just so wrong.( mocks) For most people, and I think to this day, it’s quite counterintuitive to think that the vigour is flowing through the seat around the conductor, but the vigour is, which is traveling through the field, yeah, is going relatively fast.
– So, there are a few things to notice here.
Even though the electrons depart two ways away from the artillery and towards it, by means of the Poynting vector, you find that the power flux exclusively goes one way from the battery to the bulb. This also demo it’s the fields and not the electrons that carry the vitality. – How far do the electrons go in this little thing you’re talking about, they scarcely move, they probably don’t move at all. – Now, what happens if in place of a battery, we use an alternating current source? Well then, the instructions given by current switches every half cycle.
But this means that both the electric and magnetic fields throw at the same time, so at any instant, the Poynting vector still places in these directions, from the resources to the bulb. So the exact same analysis we used for DC still works for AC. And this explains how energy is able to flow from power plants to home in power lines. Inside the cables, electrons simply oscillate backward and forward. Their motion is greatly overdid here.
But they do not carry the vigor. Outside the wires, oscillating eclectic and magnetic fields travel from the power station to your residence. You can use the Poynting vector to verify that the exertion flow is going in one direction. You might think this is just an academic discussion that you could see the exertion as disseminated either by plains or by the current in the wire.
But that is not the case, and people learned this the hard way when they started laying undersea telegraph cables.
The first Trans Atlantic cable was laid in 1858. – It exclusively worked for about a month, it never use properly. – There are all kinds of twistings when they try to send signals. – Enormous sums of aberration. They could work it at a few words per minute.
– What they found was transmitting signals over such a long distance under the sea, the pulsates became wrung and lengthened. It was hard to differentiate flecks from panaches. To account for the disappointment, there was a debate among scientists. William Thomson, the future Lord Kelvin, reviewed electrical signals moved through submarine cables like water flowing through a rubber tubing. But others like Heaviside and Fitzgerald, quarrelled it was the fields around the wires that carried the exertion and information.
And eventually, this view proved remedy. To segregate and protect the submarine cable, the central copper conductor had been coated in an insulator and then encased in an cast-iron sheath.
The iron was only meant to strengthen the cable, but as a good conductor, it interfered with a dissemination of electromagnetic fields because it increased the capacitance of the line. This is why today, most power cable are suspended high up. Even the dampen soil acts as a conductor, so you crave a large insulating gap of air to separate the cables from the ground.
So, what is the answer to our beings route light bulb question? Well, after I close the switch, the light bulb will turn on nearly instantaneously, in approximately 1/ C seconds. So, the compensate explanation is D. I reckon a good deal of beings is anticipated that the electrical arena needs to travel from the battery, the whole way down the cable which is a light second long, so it should take a second for the bulb to light up.
But what we’ve learned in this video is it’s not really what’s happening in the cables that are important, it’s what happens around the wires.
And the electric and magnetic fields can propagate out through gap to this light bulb, which is only one meter apart in a few nanoseconds. And so, that is the limiting factor for the light bulb turning on. Now, the bulb won’t receive the entire voltage of the artillery immediately, it’ll be some fraction, which are dependent on the impedance of these lines and the impedance of the bulb. Now, I invited several experts about this question, and came kind of different rebuts, but we all agreed on these key points. So, I’m gonna employed their analysis in the description in case you want to learn more about this particular setup.
If I get announced out on it and parties don’t think it’s real, we can definitely invest the resources and string up some fronts, and become our own power lines in the wilderness. – I think you’re gonna get announced out on it. – I concur, I think you’re gonna get called out.
I think that’s right. – I think it’s just kinda wild that this is one of those things that we use everyday, that almost nobody thinks about or knows the right answer to.
These moving electromagnetic waves around power lines are really what’s delivering your influence. Hey , now that you understand how electrical energy actually flows, you can think about that each time you flick on a light-colored swap. And if wishes to take your switchings to the next tier, the sponsor of this video, Caseta by Lutron, supports payment smart illuminating command, including permutations, remotes, and plug-in smart dimmers. And since one switch can domination numerous regular bulbs, you can effectively make all those bulbs smart-alecky simply by replacing the switching. Then, you can turn your light-footeds on and off working your telephone, or you can use another maneuver like Alexa or Google Assistant.
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The ignites in my power for example, turn on by themselves every evening. And this aspect gives you peace of mind that everyone in your household will ever come home to a well-lit home. And formerly you’re already in berthed, you can check which suns you forgot to turn off and do that from your phone.
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