we will discuss all important topics ;Think life without “electricity” in this modern society. Is it possible to survive without electrical energy in world of technology. Since we are science student, so it is necessary to understand the basic concept behind the word “electricity” Charge®(q) It is a very small particles present in an atom it can be either negative (electron) or positive (proton) “Coulomb” is the SI unit of charge, represented by C. Net charge (Q)–Total charge IC Net charge is equivalent to the charge contained in nearly electrons 18 6´10 Q = ne (n is no: of electron) If Q = 1C, –19 e = 1.6 ´ 10 C (negative charge on electron) Q e n = = 1 –19 1.6 ´ 10 = 100 16 ´18 10 18 = 6.2 ´ 10 18 n = 6 ´ 10 electron Current (I) Rate of flow of net charge is called current. Denoted by (I) Q t I = t is time SI unit of current is “Ampere” rep. by A. Ampere®Defined as one coulomb of charge following per second. In an electric circuit the electric current flow in the opposite direction of the flow of electron (–ve charge) conventionally. It flows from the +ve terminal of battery or cell to –ve terminal. Small quantity of current are expressed in –3 mA (milli Ampere) = 10 A –6 uA (micro Ampere) = 10 A Ammeter– It is an instrument used to measure the electric current in a circuit. It is always connected in series m a circuit + – It is represented by the symbol –––––––– A ––––––– in an electric circuit. It has low resistance. Electric Circuit– It is a closed path along which an electric current flow. A + – + – Battery (Having 3 cells) Key Ammeter Bulb The arrow shows the direction of electric current in circuit. In this circuit ammeter is connected in series. The electron can only flow when there is difference of electric pressure. For example “water flowing through a tube” It is only possible when there high pressure at one side and low at another side, then it will move from high pressure to low pressure. In case of electric current, the flow of charge is made possible due to chemical action with in a cell that generates the potential difference across the terminals of the cell. 8. Electric potential Difference– It is defined as the work done in carrying a unit charge from one point to another between the two points of an electric circuits. V = W Q V – Potential Difference W – Work Q – Net Charge SI unit of potential difference – Volts rep. by “V”