The document discusses the basic concepts of electricity including voltage, current, resistance, and atoms. It explains that voltage is electrical pressure, current is the flow of electrons, and resistance opposes current flow. Atoms are made up of electrons, protons and neutrons. An atom can gain or lose electrons to become positively or negatively charged ions. Current is defined as the conventional flow of electrons from the negative terminal to the positive terminal of a battery when a conducting path is provided.

1. 8/9/2011 Revision02 1 What is electricity?

2. Voltage: electrical pressure Current: flow of negative charges Resistance: opposition to current flow 8/9/2011 Revision02 2 There are three basic properties of an electrical circuit:-

3. VOLTAGE is electrical pressure CURRENT is a flow of electrons and occurs only if there is a voltage and a path for the electrons. 8/9/2011 Revision02 3

4. Resistance RESISTANCE is opposition to current flow. A conductor has a low resistance; an insulator has a high resistance. 8/9/2011 Revision02 4

5. 8/9/2011 Revision02 5 The Atom

6. ATOMS Electrons in energy levels The same number of Electrons as Protons No electrical charge 8/9/2011 Revision02 6

7. In electrical studies the nucleus remains the same, no protons are added or lost. The nucleus charge is never changed. An atom will only gain or lose an electron or electrons. This gain or loss will be in the outer shell. Valency shell If an atom has a charge it becomes an ION 8/9/2011 Revision02 7 ATOMS

8. Like charges repel Unlike charges attract The electrons are pushed from one object and pulled to the other object. This push/pull or force is called an emf (voltage). Units Volts, Symbol V (E) By the way, the effective speed of the electron flow is 7.5 times around the world in 1 second 8/9/2011 Revision02 8 Remember

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11. (+) ION The ion has lost an electron The total electrical charge is (+) 8/9/2011 Revision02 11

12. (-) ION This ion has gained an electron The total electrical charge is (-) 8/9/2011 Revision02 12

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. The thing to understand is: Electrons are NOT created or destroyed. They simply flow around the conducting path (circuit). 8/9/2011 Revision02 13 WHEN A SOURCE(battery) IS ADDED

14. ELECTRON FLOW When a conducting path is added the additional electrons will move to the free spaces (holes) where electrons are missing 8/9/2011 Revision02 14

15. The electrons flow from (-) to (+). ELECTRON FLOW The flow of electrons is called CURRENT. CONVENTIONAL CURRENT Flow is (+) to (-). Conventional Current flow is the Australian Standard. The unit of measurement is the ampere we use Amps The symbol is A 8/9/2011 Revision02 15 Current

16. 8/9/2011 Revision02 16 Resistance A circuit must have an opposition to electron flow. Or the very high current would cause major problems. This opposition is called RESISTANCE. Measuring Unit - Ohm Symbol - W

17. The voltage is 240 volts. V = 240V The current is 10 amperes I = 10A The resistance is 200 ohms R = 200W 8/9/2011 Revision02 17 Examples