Download Resistors Value Lesson Plan

Lesson Plan – Resistor Calculator
LO
Understanding what a resistor does
How to calculate resistors
A resistor is small but important component of your project. The components on your circuit board need to be protected, if we fed a
12 volt current from a battery directly to your small components they would be damaged. A resistor placed in front of a component
will only allow a certain current to pass through to the component on the other side.
There are many different sized resistors with different values to protect components that require a specific current to operate. So a
resistor is a bit like a hand squeezing a hose pipe resisting the flow of water/current coming out.
Task 1
To calculate the size of the resistor we need a calculator. Attached in this file is a 2 D Design drawing of a resistor chart. You will
need to fill in the appropriate colors and cut out neatly the three different wheels.
Task 2
Calculate the selected samples of resistors using your resistor value calculator
The value of a resistor is either printed in normal characters or, more usually, as colored bands. Here is an example.
The first band is red, indicating the number 2.
The second band is also red, indicating 2.
The third band is yellow, indicating 4 zeros.
The fourth band is gold, indicating 5% tolerance.
(Silver would indicate 10%, brown = 1%, red = 2%)
This resistor is 220000 Ohms in value, often written as 220k½
Example: Resistors limit current. In a typical application, a resistor is connected in series with an LED:
Enough current flows to make the LED light up, but not so much that the LED is damaged. Later in this Chapter, you will
find out how to calculate a suitable value for this resistor. (LEDs are described in detail in Chapter
Task 3 Homework
Develop an easy to remember sketch/cartoon of how a resistor works.