1. Electricity 26-Dec-151Crystal McComie

2. Electric Charge -Q Charging by Friction Static electricity is produced when a few electrons are transferred from the surface of one object to that of another. The material higher in the triboelectric series will become more positive and the lower one will end up more negatively charged. Triboelectricity can be created when one walks across a wool carpet and then touches a metal door knob. They will feel a zap of electric shock. 26-Dec-152Crystal McComie

3. Electric Forces Objects with the same charge repel while objects with opposite charges attract. The greater the charge the greater the attraction or repulsion The closer the charges the bigger the attraction or repulsion 26-Dec-153Crystal McComie

4. Charging by induction 26-Dec-154 A charge is created by the influence of a charged object but not by contact with a charged object. A conductor will be only be charged if it is insulated. The charge on a hollow conductor spreads itself all around the surface. Crystal McComie

5. Electric Field An electric field is any space in which an electric charge experiences a force. A charged object has an electric field surrounding it. 26-Dec-155Crystal McComie

6. One hazard of static charge: lightning. Lightning flashes are quite long and they pack energy in the range 10 6 -10 11 J. Clouds moving through the air become charged by friction. These charges can build up to such an extent that an electric discharge in the form of spark or flash takes place. The damage done by lightning can be quite severe. One useful application of static charge: dust extraction It is an effective way of removing dust and other fine solids. 26-Dec-156Crystal McComie

7. Current Electricity Conductors allow electric currents to flow through them with minimum opposition. They contain free electrons. Insulators (dielectrics) have electrons which are tightly bound and therefore not free. Large amounts of energy must be supplied to free electrons from the attractive forces of the nucleus. 26-Dec-157Crystal McComie

8. An electric current in a metal consists of a flow of negative electrons, whereas in other conducting media an electric current may consist of the movement of both negative and positive charge carriers. Formula: charge(Q)= current(I) × time(t) Coulombs=amperes × seconds I= Q/t t= Q/t Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source. This was the convention chosen during the discovery of electricity. They were wrong! 26-Dec-158Crystal McComie

9. Electron Flow is what actually happens and electrons flow out of the negative terminal, through the circuit and into the positive terminal of the source. 26-Dec-159Crystal McComie

10. Comparison between d.c. and a.c. 26-Dec-1510Crystal McComie

11. Alternating Current Direct Current 26-Dec-1511Crystal McComie