Electronics Course – LEDs and Resistors

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.

TestingResistance

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.

LEDcircuit

Then have a go at making your own push switch with card and foil.

PushSwitch

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.

TwoLEDs

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.

Electronics Course – Switches

Switches

Arrival Craft – Aluminium atom models 

AluminiumModel

Grid colouring sheets.

Introduction: What is electricity? Electricity is a flow of electrical charge, caused by the movement of electrons.

As you saw in your models, atoms are made up of nuclei and electrons. In metals, the electrons on the outermost shell are not very strongly attracted to their nuclei. This means that the electrons can move freely.

We’re going to make a model now to show how the ‘sea of electrons’ allows an electrical charge to flow in a metal.

 

Individual Task: each child should take a plate and stick half a dozen marshmallow halves to it. They can then sprinkle a handful of Millions sweets onto the plate. When they tip the plate, the Millions will flow, around the marshmallow halves from one end of the plate to the other.

ReGroup: Hopefully that gives you a bit of a picture of how electrons flow in a circuit.

We’re going to make another model altogether now.

Give the children a string long enough to pass all the way around the room, with ten or so beads strung on it.

If we pass this bead along the string, we can see how an electrical charge moves along a wire.

We can think of the electrons as beads moving along a string, If they keep moving round and round, the charge keeps flowing round the circuit and it can drive components that we put in the circuit.

What would happen if I cut the string?

If the string is cut, the beads cannot flow anymore.

In order for your circuits to work, they must be complete. Any break in the circuit will stop it working completely.

We’re going to make our very first simple circuits now. I have a small electronics kit for each of you, I’ll be adding new pieces to it as we progress through the course, but we’re going to start with just a few pieces.

Today we’re going to look at buzzers.

Does anyone know how buzzers make a noise?

Buzzers make a noise by vibrating. We’re going to be using piezo buzzers. These have a piezoceramic disc inside them which vibrates when an electric current passes through it.

 

Individual Task: Find the components in the kit and find out their names.

Make a circuit that switches on a buzzer when you touch two wires together.

Break for drink and snack.

 

ReGroup: You’ve made a simple circuit that buzzes when two wires touch. This is the basis for an electronic game.

Show a steady hand game you’ve already made.

I’ve looped one of my wires around the other. When the two wires touch, the buzzer sounds. But, if I can move one wire past the other, without letting them touch, then the buzzer won’t sound.

Would anyone like to have a go with my steady hand game?

Let a child try, briefly.

Individual Task: Make your own steady hand game.

SteadyHandGame

Science Club – Nervous System

Week Six – Nervous System

Arrival Craft: Paper brain model from Scholastic model book.

 

Introduction: Our brains are the control systems of our bodies. They collect information from all over our bodies and send messages back.

We use special cells to carry these messages around, does anyone know what these cells are called?

They are neuron cells.

The central part of the neuron – a long thin body – is called the axon, and it is covered with myelin sheath, which is a fatty tissue that works as an electrical insulator.

Neurons have two ends: a receiving end with dendrites and a transmitting end called the axon terminal.

There is a cell body with a nucleus in the middle of the dendrites.

Individual task: Make neurons out of pipecleaners PipecleanerNeurons

Gather Together: Does anyone know how our nerves get information back to our brains for processing?

Nerves send messages using electrical signals, these travel up the spinal cord to the brain stem.

Does anyone know where our spinal cord is?

Show on the anatomy model.

Individual task: Give out polystyrene people, so the children can put brains and spinal cords onto their models. Brains

Break for drink and snack – Try to ice brains and spinal cords onto gingerbread cookies!

Regroup: Does anyone know the names of any of the parts of the brain? Look at the brain model together.  Name the parts as you take them out, then ask the children to try and put them back in place.

I haven’t got human brains for us to dissect, I have sheep brains instead. Can anyone guess which part of the brain is much smaller on a sheep? The Cerebellum which is used for learning and co-ordination. Can anyone guess which part of the brain is larger on a sheep? The olfactory bulb, which is used for processing scents.

Individual task: Dissect brains. Children can look at pictures and try to identify regions of the brain.