Ohm's Law Experiment: Determining Resistance using Voltage and Current, Slides of Law

Download Ohm's Law Experiment: Determining Resistance using Voltage and Current and more Slides Law in PDF only on Docsity! LAB 7 OHM'S LAW Purpose: To investigate Ohm's law Before proceeding, you might want to view the lecture on electrical potential energy. Materials: DC power supply , voltmeter(0-10 V dc), ammeter(0-500milliamp), connecting wires, Rheostat, Decade Resistance Box. Discussion: Ohm's law states that I = V R !, where 'V' is the voltage measured in volts. Voltage is often referred to as the electrical potential difference between two places on a conductor. Voltage is defined as the amount of energy per unit charge that flows through a conductor. Using symbols, V ≡ E q 'I' is the current measured in amps and 'R' is the resistance measured in ohms. Current, I is defined as amount of charge per unit time that moves through a conductor. Using symbols, the definition of current is as follows: I ≡ q t Looking at the formula for Ohm's law, I = V R ! predicts that the current through a resistor is directly proportional to the voltage across the resistor and inversely proportional to the resistance. In the circuit below, R1 is a rheostat, which is another name for variable resistor. For the second resistor 'R2' we will use a Decade Resistance Box in order to predetermine various values for R2. R1 (Rheostat) When the value of R1 is altered, there will be a change in the current in the circuit. The value of the current can be read from the milliampeter ('A' in the diagram). The voltage across 'R2' will also change, and we can read its value from the voltmeter 'V'. Ohm's Law According to Ohm's law, the value of 'R2' can be determined by . You will alter the resistance of the rheostat R1 several times, (which will change the current in the circuit) and then record the corresponding current 'A' and voltage 'V' onto the data sheet. You will then make a graph of voltage versus current. The slope of the line which is the change in the vertical value divided by the change in the horizontal value, in the case , will be the value of the resistance of R2 that is predicted by Ohm's law. Fig. 1