Resistance Resistance Measuring Resistance Resistance Color Codes This

Resistance

Resistance • Measuring Resistance • Resistance Color Codes This presentation is intended to be used with Activity 6. 2. 3 Resistance.

Resistance: The opposition of current flow Tank (Battery) Faucet (Switch) Pipe (Wiring) What happens to the flow (current) if a rock gets lodged in the pipe? Flow (current) decreases

Resistance All resistors LIMIT or RESTRICT the flow of electricity. • As resistance increases, current decreases. • All components and wires have some resistance. • Materials that are good conductors offer little resistance.

Resistance External factors that affect resistance include: Thickness Diameter Larger Diameter ------- Less Resistance Smaller Diameter ------- More Resistance

Resistance External factors that affect resistance include: Resistance Length Longer ------- More Resistance Shorter ------- Less Resistance

Resistance External factors that affect resistance include: Resistance Temperature Cooler ------- Less Resistance Hotter ------- More Resistance

Measuring Resistance Ohm (Ω): The unit of measure of electrical resistance More Ohms = More Resistance = Less Current

Fixed Resistors with a value that cannot be changed Symbol for Circuit Diagrams

Reading Color Bands • Start away from the gold or silver band • Bands 1 and 2 – first two digits of the resistance • Band 3 – multiplier • Band 4 - tolerance

Eliminating Zeros • Prefixes – Kilo means ______ – Mega means _____ • How do we convert? – If resistance is between 1 and 999Ω…. . – If resistance is between 1000 and 999, 999 Ω…. – If resistance is 1, 000 Ω and up ……

Resistance Color Codes 1 st Band 1 st Digit 2 nd Band 2 nd Digit 3 rd Band Multiplier Black 0 0 1 Brown 1 1 10 Red 2 2 100 Orange 3 3 1000 Yellow 4 4 10, 000 Green 5 5 100, 000 Blue 6 6 1, 000 Violet 7 7 10, 000 Gray 8 8 100, 000 White 9 9 . 1 Gold Silver Let’s try some more! . 01 4 th Band Tolerance Band 1 Band 2 Band 3 Band 4 Orange White Brown Gold 3 9 X 10 +/- 5% 390 Ω +/- 19. 5 Ω +/- 5% +/- 10% Band 1 Band 2 Band 3 Band 4 Red Orange Gold 2 2 X 1000 +/- 5% 22000 Ω +/- 5% or 22 KΩ +/- 1. 1 K Ω %

Resistance Color Code Practice Color Calculated Converted Tolerance Accuracy Band 1 Band 2 Band 3 Resistance (± 5%) Range High ± Low

Complete the pages in your binder, identifying the color bands and calculating and converting the resistance. Next let’s actually measure the resistance to confirm our results…

Measuring Resistance • Leave the resistors on the breadboard • Touch the ends of the probe to the wires. • If your multimeter requires you to adjust the range manually: – – Start with largest resistance value and adjust it lower until you get a reading of 1. Go back one position and use that setting. In chart, record the values for each of the resistors you measured.

For further practice in reading color bands, complete the resistance chart in your engineering notes with resistors provided.

Image Resources Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from http: //office. microsoft. com/en-us/clipart/default. aspx