Download Experiment on Ohm's Law: Series Circuit and more Study notes Law in PDF only on Docsity! Experiment 15: Ohm’s Law Figure 15.1: Simple Series Circuit EQUIPMENT Universal Circuit Board Power Supply (2) DMM’s 150 ⌦ Resistor (R1) 330 ⌦ Resistor (R2) 560 ⌦ Resistor (R3) Miniature Light Bulb and Socket (R4) (1) Jumper (6) Wire Leads Figure 15.2: Schematic: Simple Series Circuit 79 80 Experiment 15: Ohm’s Law Advance Reading Text: Ohm’s Law, voltage, resistance, current. Lab Manual: Appendix B, Appendix C - DMM Objective The objective of this lab is to determine the resistance of several resistors by applying Ohm’s Law. Students will also be introduced to the resistor color code and refresh their graphing skills. Theory Ohm’s Law states that the current, I, that flows in a circuit is directly proportional to the voltage, V , across the circuit and inversely proportional to the resistance, R, of the circuit: I = V R (15.1) In this experiment, the current flowing through a resis- tor will be measured as the voltage across the resistor is varied. From the graph of this data, the resistance is determined for Ohmic resistors (R i , i = 1, 2, 3). Non- Ohmic resistors (R4, light bulb) do not obey Ohm’s Law. Ammeters are connected in series so that the cur- rent flows through them. The ideal ammeter has a re- sistance of zero so that it has no e↵ect on the circuit. Real ammeters have some internal resistance. Voltmeters are connected in parallel to resistive elements in the circuit so that they measure the poten- tial di↵erence across (on each side of) the element. The ideal voltmeter has infinite internal resistance. Our voltmeters have approximately 10 M⌦ (10⇥106 ⌦) internal resistance so that only a minuscule amount of current can flow through the voltmeter. This keeps the voltmeter from becoming a significant path for current around the element being measured. Resistors are labeled with color-coded bands that indi- cate resistance and tolerance. The first two color bands give the first two digits of the value (Fig. 15.3). The third band gives the multiplier for the first two, in pow- ers of 10. The last band is the tolerance (Fig. 15.3), meaning the true value should be ±x% of the color code value. Refer to Table 15.1 for standard color val- ues. There is no need to memorize the color codes for lab. For example, a resistor that has two red bands and a black multiplier band has a resistance of 22 ⌦. Figure 15.3: Color Code Schematic Color Number Multiplier Black 0 100 Brown 1 101 Red 2 102 Orange 3 103 Yellow 4 104 Green 5 105 Blue 6 106 Violet 7 107 Grey 8 108 White 9 109 Tolerance Gold 5% Silver 10% (No Band) 20% Table 15.1: Resistor Color Code Values
