1. Physics Activity F.A.1 BY : AASHIAPOORVAASHMEET

2. TOPIC :ELECTRIC CURRENTThe directed flow of Electrons(charges) per unit time is called electric current. Electric Current = Electric charge Time 3. FLOW OF CURRENTWe are familiar with air and water current. Similarly the electric charge flows through a conductor we say that there is an electric current in the conductor. In a torch the cells provide flow of charges or an electric current through the torch bulb to glow. 4. DIRECTION OF ELECTRIC CIRCUITWhen electricity was invented long time back , it was known that there were two types of charges : positive charges and negative charges ,but the electrons were not discovered at that time . So, electric current was considered to be a flow of positive charges and the direction of flow of the positive charges was taken to be the direction of electric current. Thus the conventional direction of electric current is from the positive terminal of the cell to the negative terminal , through the outer circuit. But the actual flow of electrons is from negative to positive. 5. HOW CURRENT FLOWS IN A WIREElectric current is a flow of electrons in a metal wire whena cell or battery is applied across its ends. A metal wirehas plenty of electrons in it.(i) When the metal wire has not been connected to asource of electricity like cell or a battery, then theelectrons present in it move at random in all directionsbetween the atoms of the metal wire.(ii) When a source of electricity like a cell or a battery isconnected between the ends of the metal wire, then anelectric force acts on the electrons present in the wire .Since the electrons are negatively charged ,they startmoving from negative to the positive end of the wire.This flow of electrons constitutes the electric current inthe wire 6. ELECTRIC CIRCUITA continuous and closed path of anelectric current is called an electriccircuit . It has 4 major components :(i) Source of current cell or battery(ii) Conductor wires(iii) Electrical device bulb, tube light.(iv) Switch or key 7. IN BRIEF(i) Source of current: It provides an electrical medium through which current flows .(ii) Conductor : It is the medium through which current passes or flows through the circuit.(iii) Electrical device is connected in a circuit .(iv) Switch or key :it makes a conducting link between cell and the bulb. 8. EXAMPLE OF AN ELECTRIC CIRCUIT 9. ABOUT ELECTRONSAccording to Bohrs model electrons are something revolving around the orbit.Charge of an electron = 1.6 * 10 raised to the power -19Mass of an electron = 9.1 *10 raised to the power -31 kg. 10. MOVEMENT OF ELECTRONS 11. NUMBER OF ELECTRONS CONSTITUTING1 COULOMB OF CHARGE?Derivation :1.6 *10 raised to the power -19C of charge = 1 electron1 C of charge = 1 191.6 * 10 =10 raised to the power 19 1.6= 6.25*10 raised to the power 18 e 12. RELATION BETWEEN I , Q AND T Current = Electric chargeTime I = Q tWhere, I = Electric current (ampere) Q = Electric charge (coulomb)t = time (seconds) 13. S.I UNIT OF ELECTRIC CURRENTThe S.I unit of electric current is AMPERE which is denoted by letter A.If we put charge Q = 1coulomb and timet = 1 second , Then the current is 1Ampere : 14. DEFINITION OF 1 AMPEREWhen one coulomb of charge flows through any cross section of a conductor in one second , the electric current is said to be 1 Ampere1Ampere = 1 Coulomb1 Second 15. SMALL QUANTITIES OF CURRENTSometimes a smaller unit of current called milliampere is also used , which is denoted by mA .The very small quantities of current are expressed in a still smaller unit of current called microampere , uA. 16. IN BRIEFSome precaution are to be taken careof while doing the numericals , wemust ensure that we have changed theunit .i.e 1 Milliampere = 1 Ampere 1000Or 1 Microampere = 1Ampere1000000 17. WHAT IS 1 COULOMB?The S.I unit of electric charge is coulomb (c) which is nearly equivalent to the charge contained in nearly 1.6 * 10 raised to the power-19 18. HOW TO MEASURE CURRENT ? 19. AMMETERCurrent is measured by an instrument called ammeter. The ammeter is always connected in series with the circuit in which the current is to be measured. For eg. If we want to find out the current flowing through a conductor we should connect the ammeter in series. As shown in the next slide. 20. PLACEMENT OF AN AMMETER 21. ABOUT COULOMBS LAWThe force between two charge bodies isdirectly proportional to the product oftwo charges q1 and q2 and inverselyproportional to square of distancebetween them.F = k q1 *q2 r *rk is the constant of proportionality. 22. SUMMARY Rate of flow of electric charges is known as electric current. Relation between electric current, charge and time= I=Qt Ammeter is used to measure current. Conventionally ,in an electric circuit the direction of electric current is taken as opposite to the direction of the flow of electrons. 23. REMEMBERWhile doing the numericals DONT forget to change the value of ampere if given in the question!