S.2 Physics Electricity Ii Notes Caltec S.2

1 TOPIC: ELECTRCITY II General Objective: The learner should be able to use the knowledge of series and parallel connection to relate resistance to the flow of current. SUB -TOPIC: Introduction to electricity (Part 2). SPECIFIC OBJECTIVES : The learner shou ld be able to; • Draw and connect electric circuits. • Describe the effects of a resistor in an electric circuit . • Connect a voltmeter and an ammeter in a circuit accurately. • Investigate and draw 1V characteristics for some components in a circuit. • Connect components in series and parallel. ELECTRCITY II ELECTRIC POTENTIAL, POTENTIAL DIFFERENCE AND ELECTROMOTIVE FORCE: Electric potential. The word potential refers to the ability to perform work. If work has to be done to move charge from one point to another, the points are said to be at different potential. The earth’s potential is taken to be zero. The potential of any given point is equal to the work done to move a small positive charge from earth up to that point. 𝐩𝐨𝐭𝐞𝐧𝐭𝐢𝐚𝐥 =𝐰𝐨𝐫𝐤 𝐝𝐨𝐧𝐞 𝐜𝐡𝐚𝐫𝐠𝐞 𝐦𝐨𝐯𝐞𝐝 In symbols: 𝐕=𝐖 𝐐 S.I unit of Electric potential is volts (V). Definition: A volt is the work done in moving one coulomb of charge from one point to another. DEFINITION: The pote ntial in volts at any point is the work done per coulomb in bringing positive charge from earth to that point. POSITIVE AND NEGATIVE POTENTIAL : In the figure below, work must be done to move positive charge from earth to conductor A. Conductor A is at a h igher potential than the earth, and its potential is taken as positive. On the other hand, work must be done to move a positive charge from point B to earth. B is at a lower potential than the earth, therefore its potential is negative. …