EEB 231 LAB 1 EEB 231 LAB 1 VERIFYING OHM’S LAW Karabo Ericah Lebopo XXXXXXXXXX Page 1 of 5 TABLE OF CONTENTS Aim……………………………………………………………………………………………2 Apparatus……………………………………………………………………………………...2...

AIM The aim of the experiment was to verify the relationship between current (I) and voltage (v) in a simple direct current circuit. APPARATUS -Digital multimeter -Variable voltage source -Connecting wires -2 resistors -Breed board


EEB 231 LAB 1 EEB 231 LAB 1 VERIFYING OHM’S LAW Karabo Ericah Lebopo 201901675 Page 1 of 5 TABLE OF CONTENTS Aim……………………………………………………………………………………………2 Apparatus……………………………………………………………………………………...2 Theory………………………………………………………………………………………....2 Procedure………………………………………………………………………………………2 Results and analysis…………………………………………………………………………...3 Discussion……………………………………………………………………………………..4 Conclusion…………………………………………………………………………………….5 References……………………………………………………………………………………..5 Page 2 of 5 LAB 1 AIM The aim of the experiment was to verify the relationship between current (I) and voltage (v) in a simple direct current circuit. APPARATUS -Digital multimeter -Variable voltage source -Connecting wires -2 resistors -Breed board THEORY Ohm’s law states that at a constant temperature , current is directly proportional to voltage or potential drop between two points in a conductor. The ratio of V/I is a constant and the constant is resistance ,R, of the conductor. V/I=R From the above equation it can be derived that : V=RI and I=V/R Ohmic materials are conductors that obey ohm’s law for example, copper. When plotting a graph of the voltage on the y axis against current on the x axis for ohmic conductors, the graph will be linear showing the proportionality of voltage and current. That implies that an increase in voltage also increases current and a decrease in voltage ,decrease the current. The gradient of the graph is the resistance of the material that is used as the conductor according to Ketin, J, B(2014) PROCEDURE A simple direct current circuit was built with two resistors in series. The equivalent resistance was found to be greater than 2kΩ. The circuit was energized from a variable voltage source of up to 30 volts. Voltage and current were measured from 6 different measurement points using the digital multimeter. A graph of voltage as a function of current was then drawn and from the graph the values of resistance was deduced. Page 3 of 5 RESULTS AND ANALYSIS Resistor 1=1.1965kΩ Resistor 2=2.1849kΩ TABLE 1 : TABLE SHOWING APPLIED VOLTAGE ,MEASURED CURRENT, MEASURED EQUIVALENT RESISTANCE AND CALCULATED EQUIVALENT RESISTANCE Applied voltage (V) Measured current (mA) Measured equivalent resistance (kΩ) Calculated equivalent resistance (kΩ) 5.0 1.4790 3.3839 3.3807 10.0 2.9550 3.3839 3.3841 15.0 4.4338 3.3839 3.3831 20.0 5.9110 3.3839 3.3835 25.0 7.3980 3.3839 3.3793 30.0 8.8960 3.3839 3.3723 SAMPLE CALCULATIONS Measured equivalent resistance= R1+ R2=1.1965kΩ+2.1849kΩ=3.3814kΩ Calculated equivalent resistance=Applied voltage /measured current =5.0V/1.4790×10˄-3 A =3.3807Ω Page 4 of 5 Gradient of line= change in voltage/change in current =(25-5)/(7.3980-1.4790) =3.389 DISCUSSION From results in table 1 as the voltage was increased the current also increased hence obtaining the resistance which is a constant. The voltage against current graph shows that an increase in voltage leads to an increase in current because the gradient of the graph is positive, indicating a positive correlation between voltage and current. The measured resistance from the graph was taken to be 3.3789kΩ and the calculated value was 3.3805kΩ. According to K.D Richard ,2011 the calculated and measured resistance can be different due to the resistance of the connecting wires and in this case that has resulted in the measured resistance being greater than the calculated one. The errors were reduced by reducing the number of connecting wires in the circuit and using shorter connecting wires with less resistance that interfered with the correct experimental results. The apparatus were switched off when making some changes in the circuit to reduce errors brought about by the increased resistance in the connecting wires due to the heating effect of current which might lead to recording incorrect of incorrect values as also supported by K. D Richard ,2011. 0 5 10 15 20 25 30 35 0 1 2 3 4 5 6 7 8 9 10 V o lt ag e (V ) Current (mA) VOLTAGE AGAINST CURRENT Page 5 of 5 CONCLUSION From the experimental results obtained it can be concluded that just as the ohm’s law states , voltage and current are directly proportional and their ratio gives the resistance. The graph of voltage against current is linear and has a positive gradient supporting ohm’s law. Measured resistance=3.3789kΩ Calculated resistance=3.3805kΩ REFERENCES Ketin ,J,B (2014). Introduction to electronics (2nd edition) Cengage learning USA Richard Budynas, K. D (2011) Advanced Electronics (3rd edition ), EL Engineering.