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# E003B electrical concepts

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### E003B electrical concepts

1. 1. 8/9/2011<br />Revision02<br />1<br />What is electricity?<br />
2. 2. Voltage: electrical pressure <br />Current: flow of negative charges <br />Resistance: opposition to current flow<br />8/9/2011<br />Revision02<br />2<br />There are three basic properties of an electrical circuit:-<br />
3. 3. VOLTAGE is electrical pressure<br />CURRENT is a flow of electrons and occurs only if there is a voltage and a path for the electrons. <br />8/9/2011<br />Revision02<br />3<br />
4. 4. Resistance<br />RESISTANCE is opposition to current flow. A conductor has a low resistance; an insulator has a high resistance. <br />8/9/2011<br />Revision02<br />4<br />
5. 5. 8/9/2011<br />Revision02<br />5<br />The Atom<br />
6. 6. ATOMS<br />Electrons in energy levels<br />The same number of Electrons as Protons<br />No electrical charge<br />8/9/2011<br />Revision02<br />6<br />
7. 7. In electrical studies the nucleus remains the same, no protons are added or lost.<br />The nucleus charge is never changed.<br />An atom will only gain or lose an electron or electrons.<br />This gain or loss will be in the outer shell.<br />Valency shell<br />If an atom has a charge it becomes an ION<br />8/9/2011<br />Revision02<br />7<br />ATOMS<br />
8. 8. Like charges repel<br />Unlike charges attract<br />The electrons are pushed from one object and pulled to the other object.<br />This push/pull or force is called an emf (voltage).<br />Units Volts, Symbol V (E)<br />By the way, the effective speed of the electron flow is 7.5 times around the world in 1 second<br />8/9/2011<br />Revision02<br />8<br />Remember<br />
9. 9. 8/9/2011<br />Revision02<br />9<br />
10. 10. 8/9/2011<br />Revision02<br />10<br />
11. 11. (+) ION<br />The ion has lost an electron<br />The total electrical charge is (+)<br />8/9/2011<br />Revision02<br />11<br />
12. 12. (-) ION<br />This ion has gained an electron<br />The total electrical charge is (-)<br />8/9/2011<br />Revision02<br />12<br />
13. 13. If the terminals have an external conducting path, the battery will continue to take electrons from the (+) terminal and place them on the (-) terminal.<br />The thing to understand is:<br />Electrons are NOT created or destroyed.<br />They simply flow around the conducting path (circuit). <br />8/9/2011<br />Revision02<br />13<br />WHEN A SOURCE(battery) IS ADDED<br />
14. 14. ELECTRON FLOW<br />When a conducting path is added the additional electrons will move to the free spaces (holes) where electrons are missing<br />8/9/2011<br />Revision02<br />14<br />
15. 15. The electrons flow from (-) to (+). ELECTRON FLOW<br />The flow of electrons is called CURRENT.<br />CONVENTIONAL CURRENT Flow is (+) to (-).<br />Conventional Current flow is the Australian Standard. <br />The unit of measurement is the ampere we use Amps<br />The symbol is A<br />8/9/2011<br />Revision02<br />15<br />Current<br />
16. 16. 8/9/2011<br />Revision02<br />16<br />Resistance<br />A circuit must have an opposition to electron flow. Or the very high current would cause major problems.<br />This opposition is called RESISTANCE.<br />Measuring Unit - Ohm<br />Symbol - W<br />
17. 17. The voltage is 240 volts.<br /> V = 240V<br />The current is 10 amperes<br />I = 10A <br />The resistance is 200 ohms<br /> R = 200W<br />8/9/2011<br />Revision02<br />17<br />Examples <br />