İzmir University of Economics EEE 0 Fundamentals of Electrical Circuits Lab EXPERMENT Ohm s Law A. Background When a voltage over a resistor is applied, there will be a flow of electrons through the resistor, called current. Georg Simon Ohm (7898), a German scientist, discovered that there is a linear relationship between the voltage over the resistor and the current through, i.e., v = R as in Fig... i(t) v(t) R v(t) = R i(t) Fig... He published his work in the book entitled 'Die galvanische Kette, mathematische bearbeitet' in 87. The S unit of the electrical resistance, the Ohm, is named after him. The Ohm s law may also be written as: v(t) i(t) = R or neglecting the time dependence simply v = R i The units of the quantities in Ohm s law are given in Table.. Table. Quantity Symbol Unit Unit Symbol Current i, Ampere A oltage v, or e, E olt Resistance r, R Ohm Ω
For an electrical component, the graphics of voltage (v) as a function of current (i) is called vi characteristics of the component. For a resistor, the vi characteristics is a linear curve. The slope of the line is R, as shown in Fig... v i R v slope=r i Fig... The vi characteristics of a resistor To obtain the vi characteristics of a resistance value of = x 0 Ω, different values to i are assigned and the values of corresponding voltages are measured (or calculated) as in Table.. Table. Current (A) oltage () ( = R ) 0 0 x 0 x 0 x x 0 = x 0 x 0 x x 0 = x 0 x 0 x x 0 = x 0 x 0 x x 0 = x 0 x 0 x x 0 = The values listed in Table.. are plotted in Fig..., volts, 0 A, ma Fig... The Characteristics of Resistor
B. Preliminary Work. For a resistance value of given in Fig..., determine the current values corresponding to the voltage values given in Table.. Plot the Characteristics on Fig... (ndicate the units of the axis!) 0 Fig.. Table.. Current (A) ( = / R) oltage () 0, volts,? Fig... For the series combination of the resistors given in Fig..6., determine the voltage values corresponding to the voltage values given in Table.. Plot the Characteristics on Fig... (ndicate the units of the axis!) Fig..6 Table.. Current (A) ( = / R) oltage (), volts,? Fig..7
. For the parallel combination of the resistors given in Fig..8., determine the voltage values corresponding to the voltage values given in Table.. Plot the Characteristics on Fig..9. (ndicate the units of the axis!) Fig..8 Table.. Current (A) oltage () ( = R ), volts,? Fig..9. Plot the results you obtained in Question, &, on the same graph over Fig..0. Comment on the results. Which has a higher slope., i.e., resistance?, volts,? Fig..0
C. Experimental Work. Firstly attach the Y006/00 module on your experiment set. You can make circuit connections as in Fig... Fig... Apply the voltages given below to your circuit respectively and measure the current values for every step. Write your measurements onto the Table.6. Calculate /A ratio for every step and fill in write to table again. (ndicate the unit of /A!) Table.6 (olts) (Ampere) A ( ).. Are the ratios invariant? What do you find as the result? Can you identify the component from this result?.. Determine the value of the resistor using (i) color codes, (ii) ohmmeter of your multimeter, Ohmmeter Result:.. Color Code Result:..
.. Are the results obtained in Part. and. consistent?. Now connect a resistor over a bread board... Measure the current values corresponding to the voltage values specified in Table.7. Calculate /A ratios for each measurement and fill in the Table. Table.7 (olts) (Ampere) ( ) Multimeter A Measurement Color Code.. Compare the results you have obtained using different ways for the resistance value?. Now measure the resistance of the series structure you studied in Preliminary Work using a bread board. Measure the current values corresponding to the voltage values specified in Table.8. Calculate /A ratios for each measurement and fill in the Table. 6
Table.8 (olts) (Ampere) A ( ). Now measure the resistance of the parallel structure you studied in Preliminary Work using a bread board. Measure the current values corresponding to the voltage values specified in Table.9. Calculate /A ratios for each measurement and fill in the Table. Table.9 (olts) (Ampere) A ( ). Plot the results you obtained in Part, &, on the same graph over Fig..., volts,? Fig.. 6. Comment on the graphical results ontained in Part. 7