LEDs and Resistors
Arrival Craft – Horra Island Sheets from Horrible Science Book.
Introduction – Did anyone get a chance to look for switches over the past week? Did you find any?
Fantastic. We’re going to have a go at making push switches today. But, we’re going to be using LEDs in our circuits, so before we start working with those, we need to talk about resistors. Does anyone know what resistance means?
Some things are conductors of electricity and some things aren’t, as you already know.
But, it’s not a binary system. There are levels of conductivity. When things conduct electricity, but not very well, we say that they have a lot of resistance.
We’re going to be looking at resistors today.
We can use multimeters to measure how much resistance things have.
Individual Task – Test various materials for resistance, use multimeters.
Regroup: Resistors are important to regulate the flow of electricity.
They work like funnels, allowing only a certain flow through.
Use funnels to show how resistors control the flow of electricity – bigger and smaller funnels could demonstrate tolerance of resistors?
We’re going to be making some more circuits today, but we’re going to be using LEDs. Has anyone used them before?
Light Emitting Diodes don’t like having too much current going through them, so we use resistors to control the flow of electricity.
Individual Task – Make a simple circuit with an LED and a resistor in it.
Then have a go at making your own push switch with card and foil.
Break for drink and snack.
Gather Together: Hopefully everyone has managed to get one LED to light.
Did anyone manage to read the current of their circuits? Did you notice anything about the currents from different parts of the circuit?
Whichever part of the circuit you read the current from, the current was exactly the same.
It can help to think of electricity as a loop all the way around your circuit.
Did anyone notice what happened when you put the resistor after your LED instead of before it?
It worked just as well, it may seem strange at first, but it doesn’t actually matter which way round the LED and the resistor are, either way the resistor regulates the flow of electricity.
I’ve got a new challenge for you now, I would like you to have a go at connecting two LEDs in your circuit.
Individual Task: Connect two LEDs in series and then in parallel.
Finish up: When you connected the two LEDs in series, what happened?
They didn’t light up because there isn’t enough current for two LEDs.
Did anyone manage to get both LEDs to light up?
How did you do it?
You can get two LEDs to light, if you connect them in parallel rather than in series. You split the current into two separate loops.
Did anyone manage to read the current of a circuit with two LEDs in it?
The current increases when you have two LEDs.
Next week we’re going to look at sensors. These are special components that allow appliances to respond to their environment. See if you can find any around your house.