Resistance Resistance Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance

Resistance Resistance Measuring Resistance Resistance Color Codes Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance Resistance Measuring Resistance Resistance Color Codes This presentation is intended to be used with Activity 6.2.3 Resistance.

Resistance Resistance: The opposition of current flow Tank (Battery) Gateway To Technology Unit 6– Lesson 6.2 – Electronics 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. Gateway To Technology Unit 6– Lesson 6.2 – Electronics 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 Thickness Resistance Diameter Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance External factors that affect resistance include: Thickness Resistance In electrical circuits, there are three EXTERNAL factors that affect resistance in the circuit. Diameter Larger Diameter ------------- Less Resistance Smaller Diameter ------------- More Resistance

Resistance Resistance Length Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance External factors that affect resistance include: Resistance Length Longer ------------- More Resistance Shorter ------------- Less Resistance

Resistance Resistance Temperature Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance External factors that affect resistance include: Resistance This is true in the case of the wire shown – the hotter the wire, the more resistance. (This is how a light bulb lights.) However, it is just opposite when talking about a thermistor, where the colder the thermistor gets, the more resistance it has. Temperature Cooler ------------- Less Resistance Hotter ------------- More Resistance

Resistance Gateway To Technology Unit 6– Lesson 6.2 – Electronics Measuring Resistance Ohm (Ω): The unit of measure of electrical resistance More Ohms = More Resistance = Less Current

Symbol for Circuit Diagrams Resistance Gateway To Technology Unit 6– Lesson 6.2 – Electronics Fixed Resistors Resistors with a value that cannot be changed First type of resistor we’ll look at is the fixed resistor. The basic materials in most fixed resistors are CARBON and GLUE. (pencil demonstration) Students should be able to recognize the diodes on the circuit pictured on the right as well as the resistors. The resistors in the right image all have a blue coating. Symbol for Circuit Diagrams

Reading Color Bands Start away from the gold or silver band Resistance Gateway To Technology Unit 6– Lesson 6.2 – Electronics 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 The fourth band (if there is one) will only be gold or silver. In this class, we only have gold banded resistors.

Eliminating Zeros Prefixes How do we convert? Kilo means ___________ Resistance Gateway To Technology Unit 6– Lesson 6.2 – Electronics 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 1,000,000 Ω and up …… Prefixes are used to eliminate ZEROS. The prefix Kilo means 1000. The abbreviation for Kilo is K. The prefix Mega means 1,000,000. The abbreviation for Mega is M. If resistance is between 1 and 999 Ω, no conversion to get rid of zeros is necessary. If resistance is between 1000 and 999,999 Ω, convert to KΩ by dividing by 1000. If resistance is 1,000,000 Ω and up, convert to MΩ by dividing by 1,000,000.

Resistance Color Codes Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance Color Codes 1st Band 1st Digit 2nd Band 2nd Digit 3rd Band Multiplier 4th Band Tolerance Black 1 Brown 10 Red 2 100 Orange 3 1000 Yellow 4 10,000 Green 5 100,000 Blue 6 1,000,000 Violet 7 10,000,000 Gray 8 100,000,000 White 9 .1 Gold .01 +/- 5% Silver +/- 10% Band 1 Band 2 Band 3 Band 4 Orange White Brown Gold 3 9 X 10 +/- 5% 390 Ω +/- 19.5 Ω 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 % Let’s try some more!

Resistance Color Code Practice Gateway To Technology Unit 6– Lesson 6.2 – Electronics Resistance Color Code Practice Color Band 1 Color Band 2 Color Band 3 Calculated Resistance Converted Resistance Tolerance (± 5%) Accuracy Range ± High Low Teacher to fill in chart with students for practice.

Next let’s actually measure the resistance to confirm our results… 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 Gateway To Technology Unit 6– Lesson 6.2 – Electronics 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.

Resistance Gateway To Technology Unit 6– Lesson 6.2 – Electronics Image Resources Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from http://office.microsoft.com/en-us/clipart/default.aspx