Transcript Electricity
Electromagnetism Home The Motor Effect 09/04/2016 Aim: • To use Flemming’s Left Hand Rule • To explain how a motor works • To construct a motor Home Fields Bar Magnets Single Science Only handout Home Opposite Poles Single Science Only Home Same Poles Single Science Only Home Fields due to Current Home Single Science Only Single Coil of Wire Solenoid Home Magnetic Field Lines There are magnetic field lines around every Magnet Electrical wire (with current flowing through it) Anything magnetic in the field will experience a force Home Wire in a magnetic field Home The Catapult (Motor) Effect Home Motor Effect If a conductor carrying an electric current moves through magnetic field lines at right angles it will experience a force. A charged particle will experience the same effect Home Fleming's left hand rule Home Increasing the Size of the Force Home The motor effect: true or false? Home Coil in a Magnetic Field Home How does an electric motor work? Home DC electric motor simulation Home 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 Worksheet Home The Motor Effect recap Home Induction 09/04/2016 Aim: •To observe and define induction •To explain how electricity is generated Home Inducing current in a wire Home What is electromagnetic induction? Current Carrying Wire + Magnetic field = Motion Motion + Magnetic field = Current in Wire Changing Magnetic field = Current in wire If they are at right angles to each other Home Inducing current in a coil Home Induction If a magnet is moved near a coil of wire a current is induced in the wire • Faster motion, bigger current • Stronger magnet, bigger current • More turns, bigger current • Change direction of motion, change direction of current Home Factors affecting induced current Home How can motion produce a current? Home 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 Home How do AC generators work? Home AC generator simulation Home Induction: true or false? Home What is a transformer? The voltage of an alternating current can be changed using a device called a transformer. A transformer contains two coils that are wound around a soft iron core. iron core The alternating current in the primary (input) coil produces an alternating magnetic field. This alternating magnetic field induces an alternating current in the secondary (output) coil. primary coil secondary coil Home How does a transformer change voltage? The voltage induced in the secondary (output) coil depends on the number of turns on the primary and secondary coils. A step-up transformer has more turns on the secondary coil and so increases voltage. A step-down transformer has fewer turns on the secondary coil and so decreases voltage. Home How are transformers used to supply electricity? Home Transformers Transformers are used to change the voltage from the Primary (input) to the Secondary (output) They only work with a.c. (alternating current) Input (Primary) Voltage = Output (secondary) Voltage Number of Primary Turns Number of Secondary Turns Example Question: Input voltage = 230 V Primary turns = 10000 Secondary turns = 500 What is the secondary voltage? Worksheet Home ??????? Home USE ME IN THIS PRESENTATION Home http://intranet.stthomasmore.org.uk/resource/Absorb%2 0Physics/Absorb%20Physics%20for%20Alevel/Absorb%20Physics%20for%20Alevel/HTML/units/080300.html Home