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

2. 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 Resistance.

3. 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

4. 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.

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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.

11. 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 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.

12. 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 +/ 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!

13. 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.

14. 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…

15. 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.

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

17. Resistance
Gateway To Technology
Unit 6– Lesson 6.2 – Electronics
Image Resources
Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from