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Cyber-chess a chess instruction site

    • Metals are good conductors of electricity - they allow current to flow easily
    • Graphite (the filling of pencils - sometimes called 'lead' but it isn't really!) is a conductor but not a very good one - it is a poor conductor.
    • Insulators make it very difficult for a current to flow at all.
    • Know how to represent simple circuits using symbols (You need to know a cell, battery, lamp, connecting wire and resistor, ammeter and switch)
    • A cell/battery provides a potential difference (in volts) which makes an electric current flow round a circuit - bigger the p.d. (voltage) the bigger the current and the brighter the bulb.
    • Think of the voltage as being a difference in 'electrical height' that makes an 'electric slope' across components - like we acted out in class with feet up on the desk!
    • A switch breaks the circuit and stops the electric current flowing
    • Short ciruits can cause high current through cells and components that might make them very hot or even ignite
    • The nature and number of components in a circuit affects current flow - the more there are in a strand the smaller the current as there are more to share out the voltage - the bigger their resistance the smaller the current because the electrons mover slower through things that have a big resistance than they do through those with a small resistance.
    • We measure current through a component with an ammeter in series with the component and potential difference across the component with a voltmeter in parallel with the component
    • The unit of current is the Ampere (usually called 'amps' - abbreviation 'A')
    • Current in a circuit is not 'used up' by components
    • Current in a series circuit is the same at each point in a strand of a circuit
    • Current in a parallel circuit is different in each strand if the resistance of that strand is different. Those currents 'add up' to go through the battery.
    • Use the term resistance 'qualitatively' - that means to explain rather than use equations - to mean opposition to flow of electricity
    • Cells and batteries are a source of electrical energy and provide an 'electrical slope' for current to flow down.
    • A battery is a number of cells connected together with regard for polarity (which way round they should be connected)
    • A cell's potential difference between its terminals has come from a chemical source and this can 'run down' with use or incorrect storage providing less of an electrical gradient for the current (i.e. the voltage stamped on a battery might not be correct - you should test it with a voltmeter)
    • A fuse is a piece of wire that is inserted in a circuit as a safety device. If the current goes above a certain value the wire will melt and then make a gap in the circuit. This will stop the current flow and prevent damage being done.