Current,IFrom Lesson 1,Current ,I is the rate of flow of charge, QCurrent = Charge TimeOrThe unit of current, I , is Ampere (A)1A= 1 C s1Current is sai!" A current flows through#######$The current is measure! %& an ammeter an! it must %e connecte!in series with the componentwhich we want to fin! the current through the component# For e'ample, if we want to measure thecurrent through a %ul% ( Potential difference( Voltage) , VAn electric circuit must ha)e a cell or some source of electrical energ& ,if there is to %e a current#The energ& to mo)e the electronsor topro!uce current we call " )oltageor potential !ifference*The potential !ifference across a con!uctor is wor+ (energ&)to carr& a unitcharge Potential difference = work= energycharge chargeOrThe unitof potential !ifference,, = ,olt(,)1 ,=1 - C1.otential !ifference is sai!" Apotential !ifference across######$The potential !ifference is measure! %& a )oltmeteran! it must %e connecte!in parallel with the componentwhich we want to fin! the potential !ifference %etween the component# For e'ample, if we want to measure the!ifference across a %ul% (7LESSO !Analysing the relationship between electric current and potential difference I = "tV = E"Example 1A %atter& is switche! on for a few moments# In that time /0 C pass through the %atter& an! the& carr& awa&1/0 -of electrical energ& # 2hat is the potential !ifference across the %atter&3SolutionExample 2A current of 4 A flowing through an electric heater for 50 minutes con)ert5#67 8 10 7 - of electrical energ& into heat energCalculate (a) the total charge circulate! through the heater(%) the potential !ifference across the heaterSolution The relation#hi$ %etween $otential difference,V and current,I in a metal conductor & Ohm'# LawTherelationship %etween )oltage, , an! current ,I in a metal con!uctor is !isco)ere! %& 9eorgeOhm is calle! as Ohm:s law#Ohm:s law state* The potential across a metal con!uctor is !irectl& proportional to the current flowing through the con!uctor , pro)i!e! that its temperature remains constant#

Or , I, ifT remains constantThe e($eriment to in)e#tigate the relation#hi$ %etween the $otential difference ,V and the current,I in a metal conductor*y$othe#i#( The potential !ifference across a metal con!uctor increasesas the current in the metal con!uctor increases# +im of the e($eriment ( To in)estigate the relationship %etween the potential !ifference ,, an! current, I in a metal con!uctorVaria%le# in the e($eriment,;anipulate! )aria%le( the currentase! on the Ohm:s law,, I, = + I+ = ,I+is replace! %&