1. Kashif Bashir1 Electricity Kashif Bashir Email: kashifbm@msn.comkashifbm@msn.com Web:www.kashifpaf.greatnow.comwww.kashifpaf.greatnow.com

2. Kashif Bashir2 Introduction Electricity is an invisible force that can produce heat, light, and motion. Electricity can be explained in terms of electric charge, current and voltage. All the materials contain two basic particles of electric charge: electron(-ve charge) and proton(+ve charge). Separate and opposite charges at the two terminals, electric energy can be supplied to a circuit connected to the battery. An atom is the smallest particle of the basic elements that form solid,liquids, and gases we know as physical substances. In an atom all the protons are in the nucleus, while all the electrons are in one or more outside ring.

3. Kashif Bashir3 Such electrons that can move freely from one atom to atom to the next are often called free electrons. The movement of free electrons that provides electric current in a metal conductor. When electrons can move easily from atom to atom in a material, it is a conductor. In general all the metals are good conductors, with silver the best and copper second. A material with atoms in which the electrons tend to stay in their own orbits is an insulator b/c it cannot conduct electricity very easily.i.e glass, plastic, rubber etc. Carbon can be considered a semiconductor, conducting less then the metal conductors but more then the insulators. Germanium, Silicon.

4. Kashif Bashir4 An element is defined as a substance that cannot be decomposed any further by chemical action. A group of two or more atoms forms a molecule.i.e H 2 O. Structure of the Atom: Energy levels Atomic Number Electron Valence Coulomb unit of electric charge(6.25 x 10 18 e - or P + ). Charges of opposite polarity attract and charges of the same polarity repel. Potential refers to possibility of doing work.When we consider two unlike charges, they have a difference of potential.

5. Kashif Bashir5 The volt is measure of the work needed to move an electric charge. when 0.7376 foot-pound of work is required to move 6.25 x 10 18 electrons b/w two points, each with its own charge, the potential difference is 1 V. Voltage is the potential diff. b/w two points. Two terminals are necessary to measure a potential difference. Potential difference across two ends of wire conductor causes drift of free electrons through the wire to produce electric current. When the charge moves at the rate of 6.25 x 10 18 electrons flowing past a given point per second, the value of the current is one ampere (A). I = Q/T. Types of electric charges for current.

6. Kashif Bashir6 Magnetic Field Around an Electric current When any current flows, it has an associated magnetic field. The magnetic field is in a plan perpendicular to the current. The iron filling just a method of making the imaginary lines of force visible. The fact that a wire conducting current can become hot is evidence of the fact that the work done by the applied voltage in producing current must be accomplished again some form of opposition which limit the amount of current that can be produced by the applied voltage is called resistance.

7. Kashif Bashir7 Conductance: The opposite of resistance is conductance. The lower the resistance, the higher the conductance.The symbol is G. and the unit is the siemens (S). The Closed Circuit: Any electric circuit has three important characteristics: 1.There must be a source of potential difference. 2.There must be a complete path for current flow. 3.The current path normally has resistance. Electron Flow Conventional Current

8. Kashif Bashir8 Direct Current (DC) Alternating Current (AC)

9. Kashif Bashir9 Source of Electricity Static Electricity by Friction Conversion of chemical Energy Electromagnetism Photo electricity Thermal Emission