Principle Of The Generator

Oh electricity light our cities at night runs many appliances in the home and provides power for electric trains where does the power come from how is it made to understand this we must follow these wires back to their stores where we'd find the huge electric generators which provide the power like so many other machines which look complicated the electric generator works by a very simple principle one which has something to do with magnet so let's begin by reviewing some of the things we know about magnet a magnet you remember can attract nails and tacks and other objects made of iron and steel a magnet can also make a compass needle move about the magnetic force of attraction acts all about it if we sprinkle iron filings over the magnet we can see how this magnetic force surrounds the Mack we call this space in which the force acts the magnetic field we know that a wire which carries an electric current also has the power to make a compass needle move about just like the magnet but the wire can act like the magnet only when electric current is passing through it like the magnet the wire has a magnetic field but only when there is an electric current in the wire these iron filings will show the magnetic field produced around the wire when the Kratt is on here in the diagram you see a cross section of the wire surrounded by its magnetic field when a wire is wound closely into a coil and a current is passed through it all of the wires magnetic force is concentrated into a small space now it can lift these objects with no trouble but when the current had switched off the coil looses its magnetic force it is the electric current flowing through the wire which gives the coil this four just as the magnet has a magnetic field about it the coil of wire has a magnetic field but only when the current is flowing through the wire it seems then that electric currents and magnetic fields may have something in common by producing an electric current in the wire we get a magnetic field let's see if the reverse is true let's see if we can get an electric current by producing a magnetic field around the wire we'll use a magnet to provide the magnetic field if trial of wire to carry the current if any and a very sensitive galvanometer which will act as a detector and tell us whether we've succeeded in producing an electric current even though it may be a very small and we'll connect the coil to the galvanometer and now we'll put the magnet into the coil what's the galvanometers needle as we move the magnet back and forth moving the magnet into the coil produces an electric current there is no current when the magnet is held stationary in the coil cooling the magnet out produces a current in the other direction only while the magnetic field is moving across the coil do we get a current in this diagram we can see the magnetic field about the magnet as the magnetic field moves across the wire the current is produced as indicated here by the brightening of the wire there is no current when the magnetic field is held near the wire and there is no current when the field is no stationary in the coil we get a current only when the magnetic field is moving across the wire in one direction or the other here you see the same effect but this time we move the wire instead of the magnet and to make the magnetic field stronger we use electromagnet instead of simple bar magnet what's the galvanometer needle register the flow of current as we move the wire through the magnetic field here is a drawing which shows the same effect the single wire moving through the magnetic field and the flow of current registering on the galvanometer you we get the same result again by twirling a coil of wire through the magnetic field as long as the wire moves in the magnetic field we get an electric current using the coil of wire rather than the single wire concentrates the effect this very simple method of producing an electric current is called electromagnetic induction and all generators however small or large use the same basic principle it involves only two strong magnetic poles to provide the magnetic field and a coil which can be turned on an act for in the actual generator the coil is made to spin but the power of steam engines are steam turbine by waterfalls or by oil engines as the great coils of wire been about in the magnetic fields within each of these generators electricity is produced by the same basic principle we've just seen from this simple method is produced and sent out over the countryside through wires to farms factories and homes to wherever electricity is needed [Music]