A resistor is a little component that usually has stripes printed on it. All it does is resist the flow of electricity — but that can be very useful.
- 2 33-ohm Resistors
- 3 Alkaline AA Batteries
- 1 Three Battery Holder
- 1 Miniature 5-volt Light Bulb
- 1 Red Alligator Wire
- 1 Black Alligator Wire
- 1 Green Alligator Wire
The colored stripes are a code telling you the resistance of the resistor. I will explain the code in a moment.
Experiment 3: Revealing Resistance
For this experiment, you need a “33-ohm” resistor with stripes that are orange, orange, and black.
Ignore the silver or gold stripe at the opposite end.
The wires at each end are called leads (pronounced “leeds”).
Put the resistor into series with your light bulb. Touch the resistor lead to the pin on the light.
The resistor limits current and drops voltage, leaving less available for the light, which glows less brightly than if you touch the red alligator clip to it directly.
Try putting two resistors in series. The light is even dimmer now. Electric current has to push through two resistors before it gets to the light.
Try putting the resistors in parallel. Now the current can flow through both of them, so the light gets brighter — although not as bright as with no resistors at all.
Understanding the Resistor Code
Each of the first two colored stripes on a resistor tells you a single digit. The third stripe tells you how many zeroes to add.
A silver stripe at the right end of the resistor means that its value is accurate within 10%. A gold stripe means 5%. Either will be okay in this workshop.
Hold the resistor with its group of three stripes on the left.
A resistor with orange-orange-black stripes has a value of 33 ohms.
Make Presents: The Resistor
Make Presents: The Resistor
Simple, commonplace, and vital to our electronic world — take a closer look at the current-fighting backbone of circuitry, the resistor, in this classic video by Collin Cunningham from the Make: Presents series.
Resistance is measured in ohms. The ohm symbol is Ω but in this workshop we’ll just say “ohms.”
Capital letter K means 1,000 ohms, so 2K is 2,000 ohms, 3.3K is 3,300 ohms, and 470K is 470,000 ohms.
Capital letter M means 1,000,000 ohms. So 2M is 2,000,000 ohms, and 1.5M is 1,500,000 ohms.
Sample Resistor Values
Could you redraw these schematics including an on-off switch?
Could you add a double-throw switch that allows you to send current through a resistor or bypass it through a wire?
Euro Style Schematics
THINK ON THIS
How Did It Work?
Two 100-ohm resistors in parallel block half as much current as one resistor. Their total resistance is 50 ohms.
If you’re wondering what happens to the current blocked by the resistor, it is converted to heat. There isn’t enough for you to feel it with your fingers, because these circuits use so little power.