Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Michael Faraday, one of the great British physicists, in 1831 discovered a way to generate an electric current without using a battery. The principle of electro-magnetic Induction which is used in generators and transformers allows electricity to be generated on a large scale. Look at the following demonstration and describe what is happening. ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ Draw on the following diagram some magnetic field lines between the poles of the magnet. Describe and explain what happens to the needle on the galvanometer when the wire is moved in the following ways: Moved vertically (A → B, B → A) Moved Horizontally ( C → D, D → C) (a) Draw the magnetic field around the bar magnet. (b) Describe what happens in this demonstration ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (c) Describe three ways in which the size of the induced current could be increased. ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ (d) Describe what would happen if the magnet were repeatedly moved into and out of the coil. ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ 1. The diagrams below each show a wire connected to a sensitive ammeter. The wire is placed in a magnetic field between opposite poles. For each diagram draw the meter reading you would expect to see. The first one has been done for you. 2. For each diagram below describe the motion of the magnet compared to diagram A on the left. You should use the following words: ‘Same speed’ ‘Faster’ ‘Opposite direction’ ‘Slower’ ‘Same direction’ ‘No movement’ When a wire cuts the magnetic field lines a current is made to flow in the wires. The direction of the current in the wire can be predicted using Fleming’s right hand rule for generators. In order to predict the direction of the current you need to know two things: The direction of the magnetic field lines, The direction of the motion of the wire in the field. Example The wire AB is part of a complete circuit and is made to cut upwards through the magnetic field between the poles. A B Use the above rule to work out the direction of the current along the wire. ____________________________________________________________ When a wire cuts magnetic field lines a voltage is induced which drives a current. A larger voltage is induced when: more wire or more coils cut the magnetic lines, the magnetic field lines are cut faster. there is a stronger magnetic field. The direction of the current in a wire can be found using Fleming’s right hand rule for generators. 1. The following dynamo can be attached to the back wheel of a bicycle in order to generate electricity to power a light. Briefly describe how the bulb is made to light up as the bicycle wheel turns. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ___________________________________________________________ [3] 2. 3. Use Fleming’s Right-hand rule to predict the direction of the current in the wire in the following diagram. A B Current flows in the direction: ________________ [1] 4. Use Fleming’s Right-hand rule to find the direction of the current in the wire in the following diagrams. Use an arrow on the wire to show the current flow. (a) (b) (c)