What is Faraday's Law of Induction? Demonstrated and Explained

[Music] hi and welcome to high school physics explained and today I want to demonstrate Faraday's law and give you a bit of an explanation as well so in front of me I have a coil and that is connected to this a meter or galvanometer and I also have a rare-earth magnet and this magnet is facing so that the north is facing outward like so what's going to happen when I insert this magnet into this coil you see the nail deflect what if I do this faster you should see that the needle deflects a greater amount so what's going on well Faraday's law in essence says that the rate of change of flux causes the production of an EMF or in other words what is conferred is an electro-motive force though in reality is talking about a voltage so when I place the magnet in the magnet has a magnetic field around that magnetic field lines are radiating around out from the magnet and as I insert the magnet into the coil the coil experiences a change in flux that is these magnetic field lines are crossing over the wires and the rate at which that occurs is causing a production of an EMF now our EMF is like a voltage so since I am producing a voltage and we now have a closed circuit I'm also producing a current as a result and so we see that in the deflection now the direction of the magnet or the direction of the relative motion between the magnetic field lines and the wires determines the direction of the EMF and hence the current so if I pull it out you're going to see it deflect the other way now what will happen if I turn my magnet over so that the South is now facing outward we're going to see the same effect with one small exception that is the deflection will be in the opposite direction why again because the magnetic field lines are now in the opposite direction now what happens if I hold it stationary you'll see no deflection whatsoever that's because we don't have any changing flux we don't have any rapidly changing magnetic field lines crossing my wire and so I have no EMF so that's a very simple demonstration of Faraday's law but let's say I don't want to use a magnet to generate a rapidly changing flux what can I do then and now in a variation of Faraday's law demonstration you'll see I still have my solenoid over on this side connected to the ammeter and there's no connection to a power supply on this side I have an ammeter a solenoid and a rheostat which allows me to control the amount of current so if I turn it on I'm going to get a deflection as you would expect a current is flowing through the solenoid and of course it will turn to zero when I turn it off now what happens if I place this on top of the solenoid like so there's no connection to the bottom solenoid let's see now what happens when I switch it on you may have noticed that a very very slight deflection takes place but the deflection lasts only momentarily now I'm going to accentuate the deflection now this is just some metal rods and I'm going to place them in the center of the core now these are not causing these two solenoids to be connected electrically in other words there is still a separation of two different circuits the only thing I've done is inserted some metal core which is going to concentrate my magnetic field lines and I'm going to demonstrate it's when I turn it on again watch what happens to the meter over here now when I switch it off what do you notice well the first thing is that the direction of the deflection is opposite to the direction of the current so the current that is going to go from this circuit is clearly going in the positive direction but the deflection here occurs in the negative direction when I switch that off you're going to see that the deflection heads in the positive direction the other thing you might notice is that the deflection only lasts momentarily it lasts for about the time that I'm switching it on but returns quickly to zero similarly when I turn it off it deflects and returns back to zero again let's explain what's going on if I just pull this out of the road when I turn this on we start with a situation where we have no magnetic field lines but when I turn the current on we are having a developing magnetic field a growing magnetic field if I place my coil in the midst of the growing magnetic field that this bottom solenoid is generating this top coil is experiencing a rapidly changing flux and the rate of which of course is determining the EMF that is generated and following on from that the current that we get but when I leave the power on the current is steady which means my magnetic field which is still there is not changing it's staying steady which means the top cart the top coil is not experiencing any changing flux what if I turn it off well I suddenly go from a very large magnetic field that this top coil is in that is going to rapidly decrease to a point of zero because of the kind of course switches off again it's not an instantaneously disappearing magnetic field it drops away which means the top coil is now experiencing a rapidly changing flux in the opposite direction hence the metal wolf deflect in the opposite direction so turning on and off rapidly will give me an alternating current I have a video on the induction coil which in essence works on the same principle switching it on and off on rapidly will cause me to have an induction that is an alternating supply in the top coil the last thing I want to mention is the concept of lenses law and lenses law is such that whatever generates the magnetic field an EMF is generated so that it opposes the change so if I were to lift this up like so and I were to turn this on this would generate a magnetic field if the current was going in a direction of that I'm going to get a current that causes the top section here to be a North Pole this one will generate an EMF but the result is is that the current that's generated will produce a pole in the opposite side it negates it so in other words we're going to get a North Pole generated at this point as a result of the North Pole being generated at this point which is the reason why the current is going in the opposite direction when I switch it on similarly speaking if I switch it off that's a very important principle lenses law because it actually is a follow-on from the law of conservation of energy now I have a video that discusses lenses law in greater detail and I encourage you to watch that but both demonstrations that are now shown you is a demonstration of Faraday's law that is the rapid change of flux with respect to time will cause an EMF and the negative sign in the in the formula of Faraday's law signifies Lenz's law well I hope that has helped you understand a little bit more in detail of Faraday's law I'm Paul from high school physics explained please like share and subscribe have a look at some of my other videos specifically I have a number of videos to deal with electromagnet any case thanks for watching bye for now well I hope that helps you understand the concepts thanks for watching please remember like share and subscribe and by the way drop a comment down below if the video particularly has been useful and finally consider supporting me fire patreon the idea is to develop resources and equipment to continue to teach physics at a high school level I'm Paul from high school physics explained bye for now

Channel: PhysicsHigh

Views: 70,655

Rating: 4.9366827 out of 5

Keywords: faraday's law, faraday's law of induction, faraday's law example, faraday's law explained, faraday's law physics, faraday's law and induced emf, faraday's law basics, faraday's law demonstration, faraday's law demo, faraday's law explanation, electromagnetic induction emf, induced emf explained, understanding faraday's law, faradays law, faraday law, faraday's law of electromagnetic induction, electromagnetic induction, faraday experiment, faraday's law experiment

Id: zRmfNvTzIhk

Length: 9min 15sec (555 seconds)

Published: Sun Mar 03 2019