The first comprehensive investigatice into the uture and measurement ef electrical tesistance was made by the Germa pysicie Okm around the year I86 afler a lengthy series of experiments "The curent in a conductor is directly proportional to the potential difference between the terminals of the cenductor and inversely proportional to the resistance of the conductor". Apparatus: 1. DC circuit training kit. 2. Set of wires, 3. DC Power supply. 4. A.V.O. meter Experiment 2 Ohm's Lav The above statement is called OHM'S LAW tfwe let P potential diferemce applied to the conductor, 1-current in the conductor, Rresistonee of the conductor Procedure: 1. Connect the circuit shown in Fig. (4). 2. Increase the voltage from (0-15) V. 3. Measure current in each steo, and then record it in table below. Objective: To stuly the relation between voltage and current Theory: In Fig1 he tunpten filament of the light bulb offers a considerable amount of opposition, or what is called ELECTRICAL RESISTANCE, to the passage of electric cument through it Because of the high resistance of the filament, the butery voltage V mat be relatively high in order to produce the amount of current I required to heat the filament to incandescence Therefore, if we express Vin volts, Iin amperes, and R in ohs, then the hasis OHM'S LAW is V supply (Voh) Eron electron flow (mA) (mA) (06) 5. 12 15 The relationship between V&I can be represented in Fig () Electric lamp iglowing) Baltory Valtage (veln Slope D.C supply electron low 100 ohm Fig (1) R denoses the amount of clectrical resistance, and in clectrical diagrams, the peesence of resistance is representing by the symbol. Using this symbel, we have redrawn Fig(1) as Fig (2), in which R denotes the "electrical resistance" of the tungsten filament in the light bulb. Curet Fig(4) Fig(3) ere are, of course, many grades of conductors (and insulators). Take, for eample. o metals such as copper and tungsten. Both are classified as "conductors," but a per wire is a better conductor than a tungsten wire of the same leagth and 1. Draw the relationship between V & I form result table. 2. What does the slopes represent in V& I relationship? 3. Why should the graphic be a straight line in result? 4. Calculate theoretically the current through the (100 1) resistor in fi recorded the calculated results in the third column of table. Discussion: meter, Tig 2 ductor: A material which gives up frec clectron carly and offers linle opposition rent tlow and the unit of conductance, is (Siemens) inverse of resistance called conductance (G) where We have already learmed that substances that offer linle resistance to the passage of uTet are called "conductors" while those that offer great resistance are called G-