Ohm's Law and Direct Current - Lab Report Example

Ohm’s Law and Direct Current Name Professor Institution Course Date Abstract Ohm’s law is a fundamental physics law. It shows the relationship between voltage and current. This report explains a step by step procedure in experimental investigation of the law. The theory, materials and methods, results and discussion, and conclusion will exhaustively explain this law. Both practical and theoretical, scientific principles support the law. Introduction Electricity involves the study of charges and their motion. An electric current results once electric charges move in a material. Ohm’s law is a statement summarizing the relationship among the current, voltage and resistance. Ohm is the name of the person who comes up with this relationship hence the name of the axiom. Alongside the experimental verification of Ohm’s law, this experiment allows familiarization with the resistor colour codes and the true values of the resistors, the tolerance and power rating of resistors, the use of measuring instruments like the digital multimeter and the AVO that measures current, voltage and resistance. Theory Ohm’s law illustrates the relationship between the current that passes through a resistor and the voltage across the same resistor for a given resistive circuit. The voltage is directly proportional to the current through the circuit. Therefore, Ohm’s law can precisely be stated as follows: If physical conditions and temperature of a metallic conductor are kept constant, the ratio of voltage across the conductor (V) to the current across the same conductor is a constant. This constant ratio (R) can mathematically be expressed by the formula: The amount of charge passing through a given point in a circuit per unit time is the electrical current. The units for current are in Amperes. One ampere is equal to a Coulomb per second. The current moves in the direction of positive charges, in the electric field. Voltage, on the other hand, is represented by negative charges. It is the potential difference and is measured in Volts. Resistance is measured in Ohms. For a metallic conductor, resistance depends of three factors. These include the length of the conductor, the cross-sectional area, the material the conductor is made of, and its temperature. This is represented by the formula: Where resistivity, the length, and the resistor’s cross sectional area Materials and Methods Equipment and Materials used includes: a. Strip Board b. Soldering Iron c. Variable DC Power Supply (PS) d. Digital Muiltimeter (DMM) e. AVO f. Conductors g. Holding Clips Pictures of Equipment Variable DC Power Supply (PS) Resistors Strip Board Digital Muiltimeter (DMM) AVO Procedure 1. The resistor and the electrical components are connected in series as in the circuit diagram, Figure 1. 2. Set the AVO to measure electric current and DMM (Digital Multimeter) to measure the voltage drop across the resistor. 3. Readjust the resistors to obtain 15 different values for voltage and current. This begins with the settings that give the smallest current in the circuit. Afterwards, the resistances are readjusting at equal intervals and the values of Voltage and Current are read. Each measurement is recorded in Table 1. 4. IMPORTANT: The variable voltage output from the power supply is set at zero and the power supply unit is switched off when the circuits are connected. Figure 1 In this figure, stands for Direct Current Power Supply, stands for Resistor Results and Discussion Table 1 below shows the values of resistor voltage between 1 and 15V, and the corresponding current. Voltage (V) Current (I) 0.0171 0 0.952 1 1.895 1.9 2.888 2.9 3.82 3.9 4.79 4.9 5.75 5.9 6.69 6.9 7.70 7.9 8.55 8.9 9.79 10 10.95 11 11.99 12 12.93 13 13.94 14 The graph below shows a plot of Voltage (V) against Current (I) The gradient of the slope is given by: Thus, resistance is Table 2 below shows experimental values of Voltage and Current for an unknown resistor Voltage (V) Current (I) 0.0053 0 0.773 0.036 1.639 0.076 3 13 3.896 18 4.86 25 5.82 28 6.77 33 7.81 38 Table 2 Figure 2 bellow shows a plot of Voltage against Current for the unknown resistor Figure 2 The plot above shows a line of best fit. The slope of this graph is given by: Thus, the resistance of the unknown resistor is = 0.19 From the graphs (Figure 1 and Figure 2), if a reasonable error margin is considered, there is a linear relationship between voltage and current. This holds true as Ohm’s law states. Conclusion In these experiments, the hypothesized Ohm’s law has been confirmed on a simple circuit. The circuit consists of power supply, resistors, ammeter and voltmeter. Voltage, V, is directly proportional to current, I. A plot of Voltage against Current has yielded a straight line graph. The slope of this graph matched the resistance value within an acceptable value of the error. Sources of errors also existed in this experiment. The measurement taken by pressing the leads to the resistor ends might not have created the best contact thus compromising accuracy. Readings made using human eyes would also be based on the judgement of human stability. References Narinder, K. (2004). Comprehensive Physics XII. Laxmi Publications LTD: New Delhi. Robert, J.H. (2003). Dc/Ac Circuits and Electronics: Principles & Applications. Thomson Learning, Inc: New York. Read More