Hello, everyone.

It's lovely to be learning science with you today.

I'm Dr.

Pemberton, and I'm really looking forward to working through the lesson with you.

Today's lesson is called Electrical Sensors, and it's a make and review lesson, meaning that we will make a sensor and then review our work.

You may have already designed a sensor or you may follow the design in the lesson.

The learning outcome for today is that you can make and review a simple electrical system to detect water levels.

It's part of our big question, how do electricity and magnetism work? And how do we see, hear, and communicate? I'm looking forward to working as a scientist and as an engineer on today's lesson.

I hope you are too.

These are the key words that we'll be using in today's lesson.

They are design, detect, sensor, trial and error, and evaluate.

Some of these words are new today, but some of them should be familiar to you already.

This slide shows the meaning of each of the keywords.

I'll explain these words as we come across each of them during the lesson, so we won't spend time going through each one now.

It's just here as a reminder and you might like to come back to it later to check that you are confident with using each of those key words.

Let's look at our lesson outline for the day.

There are two parts to the lesson.

We'll begin by building a system with a sensor.

Then we'll consider improving a design.

We're going to get going on the first part of the lesson now, building a system with a sensor.

Do you know what engineers do? Engineers generate ideas to invent, design, and build objects that matter to improve our lives.

In the picture, you can see two engineers developing their ideas.

What types of engineers do you know of? I can think of electrical engineers who work with circuits and electricity, software engineers who design code for computers, and I can think of structural engineers who design buildings.

Did you come up with any of those or maybe some others? Now, Andeep and Sofia want to build something to improve the lives of children who walk miles each day to collect fresh water from a well.

In lots of countries in the world, families don't have taps at home from which they can get their water.

So the task of getting water is a big part of their daily lives.

So Andeep and Sofia have designed a sensor to detect the water levels in the well.

Sensors are devices that can detect changes.

Andeep says, "We have designed a system with a sensor, which includes a circuit with a bulb." And Sofia responds, "When the water level in the well rises, a switch closes to complete the circuit and the bulb is lit to show that there is enough water in the well." And Andeep pass, "When the water level is low, the switch opens to make the circuit incomplete and the bulb is not lit." Okay, so if the light is on, there's water available in the well, and if it's off, there's no water.

And if the children can see this light back in their homes, then they can avoid having to make the walk all the way to the well only to find out that it's empty.

That is useful and it would improve lives.

Let's think about the engineering design process.

When engineers invent and build things, they come up with their initial ideas and then they develop them into a design.

They build their designs, then test them to see if they work as they had hoped.

Often, they need to make changes and improve the first design before they develop the final product.

And in this picture, you can see an engineer working on a design.

Let's check what we've learned so far by trying a question.

This one's about engineers.

Why do engineers have to generate ideas? Is it, A, to repair and fix objects that matter, B, to invent, design, and build objects that matter, or C, to advertise and sell objects that matter? What do you think? Well done if you chose B.

Engineers have to generate ideas to invent, design, and build objects that matter.

Let's carry on with our learning and get back to the water sensor.

Andeep and Sofia have drawn their initial design.

Let's have a look at it.

Let's start with the drawing on the left showing the sensor when there's a low water level.

You can see that they have the well shown as a rectangular container with water in it.

And then if we look towards the bottom, there's a cork covered in foil floating on the water, and it's got a wire attached to it.

That wire leads up to a circuit which has a battery and a bulb.

Then on the other side of the bulb is another wire which dangles down into the well.

Do you know why they've covered the cork in kitchen foil? It's to do with electrical conductivity.

Cork is an electrical insulator, so electricity doesn't travel through it easily, and it would break an electrical circuit.

But kitchen foil conducts electricity, so it can be used to complete a circuit.

And in this case, when the water is low, the circuit is incomplete anyway, so the light doesn't light up.

But let's compare that with the drawing on the right hand side where the water level is high.

Here, the foil covered cork has floated up on the water and is now high enough to be touching the dangling wire.

This completes the circuit and the light turns on.

And the explanation says, when the water rises, the cork covered in foil floats up, touches the hanging wire, and completes the circuit to light the bulb.

Ah, but Jacob said he's worried about the safety of this design.

Do you know why that might be? Laura explains.

She says, "We can't have an electrical device working around or near to water." Strict safety rules must be followed when we use electrical components near water.

This is because water can contain dissolve minerals which conduct electricity.

That's why we shouldn't take electrical equipment into our bathrooms. So now we're worried that it could be dangerous to have the wire from the circuit going up and down on the cork right next to the water.

Andeep and Sofia need to come up with a way that the circuit and the sensor could be built more safely.

Andeep says, "We need to avoid having the circuit attached to anything on the water." And Sofia thinks, "I think we need to try and build our design to see if it can be made any safer." I think that's a good idea too, and it's how engineers work.

They come up with a design, then they try it and improve it, so they might build it even though they know it's not perfect, because once they've got a model, it will help them understand the whole system.

Let's check our understanding by trying another question.

This one's a missing word question.

It says, strict safety rules must be followed when using blank near to water.

What could the blank be? Is it A, magnets, B, corks and foil, or C, electrical components? What do you think? Well done if you chose C, electrical components.

So the whole sentence would be strict safety rules must be followed when using electrical components near to water.

Now, it's your turn to do some science.

You are going to build your first version of a sensor to detect water levels in a well.

You could adapt Andeep and Sofia's design or you could use your own.

You may have already drawn a design or you may want to do so now.

But before you begin with your building, you need to ask an adult to check your design to make sure it'll be safe and that they're happy for you to start building.

At this stage, do not add any water to your well.

Just build the bits for the sensor.

It is time now for you to pause the video and work on your sensor.

When you finished, come and rejoin me for the next part of the lesson.

Welcome back.

How did you get on? Your design may look like this or it may be completely different.

The children say, "This is our sensor.

It's not connected to the circuit in this photo." In the photo, you can see that they've used an old lemonade bottle to make the well.

Then looking at the bottom of the well, you can see the cork covered in foil which is attached to the wire.

And you can also see the wire that's dangling into the bottle that's designed to complete the circuit.

Let's move on to the second part of the lesson.

This part is all about improving a design.

Science is about thinking creatively to try and explain how things work.

Sofia and Andeep know they need to think creatively to try and improve the safety of their design.

Let's have a look at this photo of their new design.

This is the improved version.

I can see that the old wires have gone and they've been replaced by contacts made from aluminium or kitchen foil folded into thick strips.

So these aren't attached to the cork.

The cork is still at the bottom floating in water, and it looks like, when it floats up, it will touch both of the contacts rather than being sellotaped to one of them.

What does Andeep say? "We've added two aluminium foil contacts at the top of the well.

These will be attached to the wires in the circuit.

When the cork rises up, it will touch the contacts and complete the circuit." Yes, that seems much better not having a wire attached to the cork.

Let's check our understanding with a question.

This one's a true or false question.

Engineers only use maths and science, so they do not need to think creatively.

What do you think? That's false.

They do need to think creatively.

But why do they need to think creatively? Is it because, A, they need to think creatively to produce artwork and poems, or B, they need to think creatively to explain how things work? Well done if you chose B.

Engineers use maths and science, but they also have to think creatively to explain how things work.

Let's carry on and learn some more.

So once they've got their initial design, engineers use trial and error to improve their designs.

And you can see an engineer here testing a design in a picture.

Trial and error is when we keep trying and we use the errors we make to learn until we get it right.

We all know that making mistakes is how we learn.

Engineers know that they must not give up and they must just keep trying different solutions to solve problems. Let's look at some examples of this.

Engineers who design aeroplanes test different wing shapes and models before deciding on the best one.

Also, engineers who design cars and other vehicles use trial and error to investigate different materials to improve safety and efficiency.

Similarly, engineers test different designs in models of bridges to find the strongest structures before they build the final full size bridge.

And computer engineers use trial and error with different components and algorithms to come up with the best programmes and apps.

Let's check our understanding with another question.

This one's a multiple choice question.

What is the name of the process where people use the mistakes they make to learn until they get it right? Is it A, error and improvement, B, trial and error, C, trial and improvement, or D, trial and modify? Well done if you chose B, trial and error.

So trial and error describes the process where people use their mistakes to learn until they get something right.

Let's carry on and think a bit more about engineers and the design process.

After they've used trial and error to improve their work, engineers evaluate their designs and inventions.

This helps them and other engineers to make improvements for future inventions.

Here we can see an engineer evaluating their thinking.

They say, "On this model, the wings are strong enough, but they do not allow the plane to move quickly." So after a bit of thinking, the engineer decides, "My design will use the same materials, but I will try different shaped wings." They've evaluated the good bits of their design and they'll keep these.

And then they've also thought about the bits which need improving or changing.

Here we can see that the children have been evaluating their sensor.

They've improved it, but it's still not perfect.

Sofia says, "When the cork floats up, it sometimes moves around in the water so it doesn't always touch the contacts for the circuits." You can see that's what's happened in this picture.

The corks at the same height as the contacts, but it's sitting at the side of the well, not in the middle, so it's not actually touching the contacts.

So knowing that, how would you evaluate their design so far, and what would you do next to solve the problem? Sofia suggests, "We could design and build a circular ring covered in foil to float in the water, instead of a small cork." Andeep suggests, "We could design and build a holder in the well that makes the cork float up and down in the right place to touch the contacts." Do you have any other ideas? Let's do our final check for understanding to see what we've learned.

This one's another multiple choice question.

It says, which of the following are examples of working by trial and error? Is it, A, making a wheel, then testing it and adapting the design after testing it, B, making a wheel, then advertising it using the design, or C, making the wheel, then adapting the design before testing it? Well done if you chose A, making a wheel, then testing it and adapting the design after testing it is a good example of working by trial and error.

There's no point doing C.

If you adapt the design before you've tested the original one, you don't know what needs to improving.

Okay, now it is time again for you to do some science and engineering with your final task.

There are two stages to this task.

In the first stage, you need to use trial and error to test and improve your sensor to detect the water levels in the well.

Then when you've done that, you need to evaluate your system by answering these questions.

Does your sensor detect changes in the water level? Does your sensor open and close with a switch? Does a change in the water level cause a light to turn on? Does your system work reliably? And finally, would you change your system in any way? For this time, we'd like you to answer your questions in complete sentences.

So now pause the video and go and do this and then come back and join me for the final part of our lesson.

How did you get on? Were you pleased with your final sensor? This is Andeep and Sofia's final design.

They made a plastic tube and stapled it to the wall of the well.

So they used Andeep's idea of controlling where the cork went.

The tube was just a tiny bit bigger than the cork and they put the cork inside it.

So the tube controlled the movement of their cork up and down within the well.

And then they positioned the contacts in the place where it would definitely touch them.

And you can see that in this second photo.

You can see the contacts are dangling into the tube that the cork's floating up and down.

Your final version might be like this or it might be completely different.

Let's look at their evaluation.

The first question was, does your sensor detect changes in the water level? And they have answered, "Our sensor can detect changes in the water level." The second question, does your sensor open and close a switch? And they answered, "We made a tube from rolled up plastic and stapled this to the inside of the well with the cork inside.

As the water level rises, the cork floats up.

It acts as a switch because when the water level is high enough, the cork closes the gap to complete the circuit and it lights up the bulb." Let's look at the third question.

Does a change in water level cause a light to turn on? And they said, "The change in water level does turn the light on, but sometimes when the cork seems to be touching both wires, the light does not come on." Ah, this leads to the next question, does your system work reliably? And they've written, "The cork sometimes does not touch the wires enough," or the contacts I think they mean, "to complete the circuit." Finally, would you change your system in any way? And for this one, the children said, "If we made another one, we'd try and make better contacts between the cork and the wires." I wonder if your evaluation was similar.

I wonder if you'd change anything if you were to redesign your sensor.

Was yours reliable? Well, we're coming to the end of the lesson, so let's look at the summary to remind ourselves of what we've learned.

Engineers develop ideas to invent, design, and build objects that matter.

Strict safety rules must be followed when using electrical components near to water.

Science is about thinking creatively to try to explain how things work.

Trial and error is when we try different ways to solve a problem and learn from our mistakes.

Thank you for joining me for this lesson.

I've enjoyed learning about sensors together, and I hope that you enjoyed working like an engineer and a scientist by using trial and error to build and improve your own sensor.

Well done for your hard work.