* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 10. Motors and Generators
Magnetic monopole wikipedia , lookup
Geomagnetic storm wikipedia , lookup
Electrical resistance and conductance wikipedia , lookup
Magnetometer wikipedia , lookup
Earth's magnetic field wikipedia , lookup
Mathematical descriptions of the electromagnetic field wikipedia , lookup
Giant magnetoresistance wikipedia , lookup
Magnetotactic bacteria wikipedia , lookup
Magnetoreception wikipedia , lookup
Friction-plate electromagnetic couplings wikipedia , lookup
Electromotive force wikipedia , lookup
Skin effect wikipedia , lookup
Electromagnetic field wikipedia , lookup
Magnetohydrodynamics wikipedia , lookup
Force between magnets wikipedia , lookup
Induction heater wikipedia , lookup
Electromagnetism wikipedia , lookup
Lorentz force wikipedia , lookup
Electricity wikipedia , lookup
History of electrochemistry wikipedia , lookup
Magnetotellurics wikipedia , lookup
Alternating current wikipedia , lookup
History of geomagnetism wikipedia , lookup
Ferromagnetism wikipedia , lookup
Superconducting magnet wikipedia , lookup
1 of 29 © Boardworks Ltd 2007 2 of 29 © Boardworks Ltd 2007 Electromagnetism and movement What is the link between movement, magnetism and electric current? 3 of 29 © Boardworks Ltd 2007 Wire in a magnetic field 4 of 29 © Boardworks Ltd 2007 Changing the direction of the force The direction of the force acting on a wire in an electromagnetic field can be reversed by: reversing the current reversing the magnetic field The direction of the force is therefore relative to both the direction of the magnetic field and the current. 5 of 29 © Boardworks Ltd 2007 Fleming’s left-hand rule It is possible to predict the direction of the force acting on a wire – its motion – if the direction of the current or the magnetic field are known. Fleming’s left-hand rule is used to do this. thuMb = Motion First finger = magnetic Field seCond finger = Current 6 of 29 © Boardworks Ltd 2007 Increasing the size of the force 7 of 29 © Boardworks Ltd 2007 Coil in a magnetic field 8 of 29 © Boardworks Ltd 2007 The motor effect: true or false? 9 of 29 © Boardworks Ltd 2007 10 of 29 © Boardworks Ltd 2007 What are electric motors? How many items do you own that contain an electric motor? An electric motor is a device that converts electrical energy into mechanical energy to produce a turning effect. Most motors are powered using direct current (DC), which is produced by cells and batteries. Motors powered by mains electricity use alternating current (AC). These motors use electromagnets rather than permanent magnets. 11 of 29 © Boardworks Ltd 2007 How does an electric motor work? 12 of 29 © Boardworks Ltd 2007 DC electric motor simulation 13 of 29 © Boardworks Ltd 2007 How do we increase motor strength? Would the same strength motor be used in both of these? How can the strength of an electric motor be increased? increase the current flowing through the coil increase the strength of the magnet increase the number of turns on the coil 14 of 29 © Boardworks Ltd 2007 15 of 29 © Boardworks Ltd 2007 Inducing current in a wire 16 of 29 © Boardworks Ltd 2007 Fleming’s right-hand rule It is possible to predict the direction of the induced current produced by a generator if the direction of the force (or motion) or the magnetic field are known. Fleming’s righthand rule is used to do this. thuMb = Motion First finger = magnetic Field seCond finger = Current 17 of 29 © Boardworks Ltd 2007 What is electromagnetic induction? When current flows through a wire held in a magnetic field, a force is created that moves the wire. The opposite is also possible: if a wire is moved across a magnetic field, a current is produced. This is called electromagnetic induction. Induction also occurs if a magnet is moved in a coil of wire, or if a coil of wire rotates in a magnetic field. In all these methods of inducing a current, the wire and magnetic field move perpendicular to each other. If they move parallel to each other, no current is induced. 18 of 29 © Boardworks Ltd 2007 Inducing current in a coil 19 of 29 © Boardworks Ltd 2007 What are generators? A generator is a device that converts mechanical energy into electrical energy. It is the opposite of an electric motor. Power stations use generators to produce electricity on a large scale. Mechanical energy is provided by rotating turbines that can be powered by: high-pressure steam – in coal, oil, gas and nuclear power stations wind – in wind turbines falling water – in hydroelectric power stations 20 of 29 © Boardworks Ltd 2007 How do AC generators work? 21 of 29 © Boardworks Ltd 2007 AC generator simulation 22 of 29 © Boardworks Ltd 2007 Increasing the size of the induced current How can the size of an induced current be increased? increase the speed at which the coil rotates increase the strength of the magnetic field increase the number of turns in the coil increase the total area of the coil. In a power station generator, an electromagnet is often used as this can provide a stronger magnetic field than is possible with a permanent magnet. 23 of 29 © Boardworks Ltd 2007 Factors affecting induced current 24 of 29 © Boardworks Ltd 2007 Induction: true or false? 25 of 29 © Boardworks Ltd 2007 26 of 29 © Boardworks Ltd 2007 Glossary alternating current – A current that constantly changes direction. It is produced by most electrical generators. commutator – The part of a motor that enables the coil to rotate using direct current. direct current – A current that always flows in the same direction. It is produced by cells and batteries. generator – A device that converts mechanical energy into electrical energy. induction – Generating a current in a wire by moving the wire in a magnetic field, or by moving a magnet inside a coil. motor – A device that converts electrical energy into mechanical energy. slip rings – The parts of a generator that enable the rotating coil to produce alternating current. 27 of 29 © Boardworks Ltd 2007 Anagrams 28 of 29 © Boardworks Ltd 2007 Multiple-choice quiz 29 of 29 © Boardworks Ltd 2007