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The Physics of Electricity and Magnetism Magnetic Induction of Current 9-12 Science Std: Phys 5h It was a very special discovery…. When Oersted found that current in a wire made a magnetic field….. Physics was changed from then on…. It was a very special discovery…. But then scientists asked….. If electricity can make a magnet… Can a magnet make electricity? Then in 1831……. Two scientists found a way to do it! In England And here in the U.S Michael Faraday Joseph Henry They both found a way to do it at the same time in different places Before that…. The only way to make an electric current was.. Dissolving special metals in acids Which was very expensive and dangerous But now….. We can make electricity any time, anywhere! To make Electricity we need: N S A magnet And a piece of wire. Wait a second…… Didn’t we say before…. N Electricity (a current) S To make a magnet we need: Yes, we did! And a piece of wire. Wait a second…… In fact, we said…. As long as charged particles are moving… A magnetic field is made using the Right Hand Rule S And the current is going through a wire N Like with an electrical current Wait a second…… But now we are saying….. To make an electrical current…… You take a magnet S And you use a piece of wire… N And you get an electrical current! So how does this work….. When we made the magnetic field…. The charged particles were moving… Which is an electrical current And they were moving because of an electric field or voltage potential… So how does this work….. So now to make the electrical current….. We still need some movement….. But this time instead of moving the current to make the magnet…. So how does this work….. So now to make the electrical current….. We still need some movement….. We move the magnet to make the current! N S So how does this work….. When we move the magnet across the wire…. S And the voltage makes an electrical current in the wire N The lines of the magnetic field move past the wire…. As the magnetic field lines pass the wire It makes a voltage potential in the wire Let’s see this in action…. Demonstration time! On the front desk is a meter called an ammeter This is a meter that can measure the amount of current And it can show the direction the current is flowing Let’s see this in action…. Demonstration time! The more the needle moves on the meter… The more current is flowing in the wire The direction the needle moves… Shows which direction the current is moving Let’s see this in action…. Demonstration time! The ammeter is hooked up to a coil of wire We use a coil because the more wire – the more current is made Let’s see this in action…. Demonstration time! Then we take a magnet and move it through the coil of wire… While the magnet is moving, watch what happens to the ammeter…… N S Can the amount of current change? Yes it can…… The amount of current depends on… The amount of wire A little wire…… Makes a little current A lot of wire….. Makes a lot of current Can the amount of current change? Yes it can…… The amount of current depends on… The amount of magnetic field A small magnet A big magnet N N S S Makes a small current Makes a big current Can the amount of current change? Yes it can…… The amount of current depends on… How fast the magnet moves Magnet moves slowly N S You get a small current Move the magnet fast N S And you get a large current Can the amount of current change? Yes it can…… So remember……. The amount of current depends on: 1. The amount of wire 2. The size of the magnet 3. And how fast the magnet moves N S So where can we use this? Where are some places we can use this? But we can also use it to power a flashlight without batteries To make electricity that we use at home Important Points….. Changing magnetic fields make electric fields Electric fields are voltages Electric fields or voltages can be seen by using a voltmeter Electric fields or voltages can make electrical currents in conductors Electrical currents in conductors can be seen by using an ammeter So if you would like to take a closer look….. You can come up and give it a try