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.

So let's get going.

Today's lesson is called electrical sensors and it's a design lesson.

I wonder if you've done much designing in the past, and I wonder if you know what a sensor is.

The learning outcome for today is that you can design a simple electrical circuit to detect water levels.

It's part of two of our big questions: how do electricity and magnetism work and how do we see, hear, and communicate? I'm looking forward to working as a scientist with you to learn more about this.

I hope you are too.

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

Switch.

Circuit.

Sensor.

Detect.

And design.

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

This slide shows the meanings of each of the keywords.

I'll explain the 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're confident using each of those words.

This is our lesson outline.

There are two parts to today's lesson.

We'll begin by learning about sensors.

Then we'll find out how people use sensors.

We're going to get going now on the first part of the lesson, sensors.

Ah, here's Andeep.

He says, "Some things in my house turn on and off without using a switch." Sofia's noticed something in her house too.

She says, "Our heating turns on when it gets too cold." Andeep's also noticed that at his house, the outside light turns on when the cat passes.

Can you think of anything in your house that turns on or off without you using a switch? I can't think of anything at home, but I've been in school and the lights have turned on as I've entered a classroom.

Do you know how this happens? Some electrical circuits are controlled by switches which are connected to sensors, and this picture shows a motion sensor.

The sensors are in the two little bulbs that stick out at the bottom and they can detect movement.

Sensors are devices that can detect and monitor changes in things like light, temperature, motion, which is also movement, sound, or pressure.

Circuits like this can then be switched on or off when these things change.

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

What do you call devices which can detect changes in things like light, temperature, motion, sound, or pressure? Well done if you chose B, sensors.

So sensors are devices which can detect changes in things like light, temperature, motion, sound, or pressure.

Let's carry on with our learning.

There are sensors all around us.

They're used in many of our everyday appliances.

This photo shows a motion sensor.

So the sensor is the little rounded bit that's stuck to the ceiling on the right hand side of the picture, and it also shows some lights.

Those are the square panels on the left hand side.

This image shows a mobile phone.

So the lights on the left turn on when the motion sensor detects movement in the corridor.

So that must be what happened in the school I visited where the lights seemed to come on magically when I opened the door.

Similarly, the mobile phone in the second picture lights up when a motion sensor detects that it's been picked up or it's been moved.

In this way, sensors make our lives easier by automatically responding to the world around us.

Motion sensors detect movement, which triggers a switch to complete a circuit or make a gap in a circuit.

So if they complete a circuit, that means the motion will make something come on, like a light, and if they make a gap in a circuit, that means that the motion will make something turn off.

These sensors are often found in security systems and burglar alarms. Sound sensors detect noise, and that can also be used to trigger a switch in a circuit.

They're commonly used in entertainment systems and smart devices in our homes.

I wonder if you've ever tried using a smart speaker.

This picture shows the temperature control system on the end of a radiator.

Have you ever seen one of these? Temperature sensors are used in monitoring heating and cooling systems, and they can trigger warning buzzers when fridges become too warm.

This picture shows a smoke detector.

Smoke and fire alarms rely on sensors to detect smoke or heat in the air, and then they can trigger warning alarms so that the people in the building know that something's happening and they need to act.

There's another type of sensor called a light sensor, and light sensors are used to provide information to cameras, automatic doors, and solar panels.

So with an automatic door, the sensor detects that the light has decreased, and this might be because a person has blocked it.

So if a person has blocked the door, it means the automatic door needs to be opened, so the sensor would trigger the door opener.

With movable solar panels, the sensor would detect the light levels and they'd find out where the highest light level was coming from so that the panels could then be programmed to turn to face the highest light levels.

Let's test our understanding with another question.

Which of the following everyday items are likely to include sensors? Is it A, stairs; B, mobile phones; C, tables; or D, burglar alarms? That's right, it's B, mobile phones and D, burglar alarms. Do you remember the mobile phone had a sensor to detect motion so the light would turn on when it's picked up, and some burglar alarms also have sensors for motion or movement.

Now it's your turn to do some science.

This is your first challenge for the day.

You are going to try some activities to help you explore the types of sensors which are found in everyday appliances and systems. Let's look at the appliances we have.

There's a mobile phone, a heater, security lighting, a fridge freezer, and smart speakers.

Your first task is to match the appliances to the type of sensor you think it has from the list on the right.

So you can choose from a temperature sensor, a motion sensor, and a sound or noise sensor.

Now I can see that there are only three sensor options, so some of these will be needed more than once.

Once you've matched the sensors to the appliance, you need to move on to the second part.

Here you'll need to explain the role of the sensor, so that means you'll need to think about what it does and why.

And to do this, you'll need to think about the job that each appliance does and how that sensor could help it work.

Finally, when you've chosen the sensor and its role for the appliances, try to add a couple of your own.

Think of devices you use at home and whether they appear to do anything automatically.

Could it be due to a sensor? It is time for you to pause the video and try the tasks.

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

Welcome back.

How did you get on and what did you find? Your answers for the appliances given in the question should be similar to these.

The mobile phone has a motion sensor to detect if someone picks it up.

The heater has a temperature sensor to make the heating come on when it's too cold and turn off when it's too hot.

The security lighting has a motion sensor to turn a light on when someone moves.

The fridge freezer has a temperature sensor to make a buzzer sound or make a noise when the fridge is too warm.

That could be if the door's accidentally been let open, so it would let the user know that they need to shut the door.

And finally, the smart speaker has a sound or a noise sensor to receive instructions from the user.

Did you work all of those out? I wonder what extra devices you added to your table.

Now we're gonna move on to the second part of our lesson.

This section is all about using sensors.

Some appliances have many sensors.

Washing machines, for example.

Now washing machines have sensors to detect lots of things.

They have a sensor to detect the water level so it doesn't get too full and so that there's enough water to actually do the washing.

They have a sensor to monitor the temperature of the water to make sure it's just right for cleaning.

And they also have another one to detect the weight of the washing load inside the machine.

And with some really clever machines, this can be linked to the detergent, so the machine will add detergent depending on how many clothes there are in the machine.

Ah, but Andeep is worried.

He says, "You shouldn't use electric circuits near water, so how can you have electric sensors for water?" That's a really good point, Andeep.

It's not safe usually to have electricity near water.

Ah, here's something else that uses electricity near water.

Kettles have sensors to make them turn off when the water boils.

Like Andeep was worried about the washing machine, Sam is worried about the kettle.

She says, "In a kettle, the water is close to the electricity.

How can that be safe?" Well, when scientists design appliances which work with or near water, they have to really consider the materials they use to make them safe.

How could you make sure a kettle is safe? This means that the part where the electric circuit is must be sealed off from the water holder.

You can see in the picture that the electric circuits are all in the bottom of the kettle.

The parts of the kettle that the water touches and the parts that we touch must be made from an electrical insulator, those bits I've circled.

So the sensors that kettles have are called moisture sensors and they detect water.

Appliances must be designed and used in a way to ensure that the circuit does not come in touch with the water.

Let's look at my kettle to see the parts we've talked about.

So I've got my kettle here and it's got two parts.

This is the jug.

The water goes in the top here, and that's all sealed off and has no electrical circuit inside it.

There is an electrical circuit in the very bottom with a contact here, but this bit doesn't ever get plugged into the mains electricity.

This is the base of my kettle, and this is the bit that gets plugged in.

You can see the cable has got an insulated layer on it and the plug has got an insulated layer.

And then this base has got a circuit in it, and this is where the circuit is that the electricity goes into.

And then this contacts to the bottom of the jug and causes the bottom of the jug to heat up, but it never touches the water inside the jug.

And in that way, the design keeps us safe.

Let's think where else we might use moisture sensors.

Moisture sensors are used in farming to monitor how dry soils are.

So if the soil gets too dry and the sensor measures that, then it might trigger a hose or a sprinkler to turn on.

They're also used in buildings to find out if rooms are dry enough and check whether there's mould growing in them.

Moisture sensors are also used to detect leaks in pipes, pipes outside or pipes in buildings.

And finally, they can detect water levels in large containers or tanks.

Let's see what you can remember with a couple of questions.

This one's a true or false question.

Do you think this statement is true or false? Electrical circuits can never be used with appliances that are used with or near water.

What do you think? That's right, it's false, but can you explain why it's false? Is it because A, it's not dangerous to use electricity near water, or B, because strict safety rules must be followed when planning to use electrical circuits near to water? Well done if you chose B.

Electrical circuits can be used with appliances that are used near or with water, but you must follow strict safety rules because it's dangerous to mix water with electricity.

Let's carry on and learn some more.

Andeep and Sofia have been reading about a town where the children have to walk to a well every day to collect fresh water.

The walk is very long, and sometimes, when they get there, the children find that the well is empty.

In these cases, they waste a lot of time and energy making the journey.

Sofia's been thinking about this and she says, "I wonder if I could make a sensor to detect changes in the water level in the well so the children would know if there's enough water before they left home." I think that sounds like a great idea, Sofia.

What do you think she could do? Well, Sofia's idea could improve the lives of the children, so she's really thinking like an engineer.

Engineers design, invent, and build things that matter and improve lives.

To do this, they develop their initial ideas and test them.

Then they make changes and improve them.

And in this picture you can see some engineers, and it looks to me like they're discussing an initial design.

Engineers can look at existing and successful designs to give them ideas about moisture sensors.

This photo shows the fuel gauge from a vehicle.

People who drive vehicles with fuel tanks rely on this gauge to tell them when the tank is empty.

So the sensor inside the tank detects how much fuel is left in it, and then that's shown by the arrow on this gauge.

So the driver knows they're running low and they need to refill the tank.

There are also sensors to help people with visual or sight impairment.

Someone with a visual impairment can safely make a hot drink with the help of a liquid level indicator, which makes a noise when the cup is full.

Isn't that an amazing design? So Andeep and Sofia are thinking about their own design.

Andeep says, "We could design a system which includes a circuit with a bulb." Okay, so the bulb would be the indicator whether there's enough water or not.

Sofia has a suggestion too.

"When the water level in the well rises, a switch closes to complete the circuit and the bulb becomes lit to show that there's enough water in the well." And then Andeep adds, "So when the water level is low, the switch is open and the circuit is incomplete, so the bulb is not lit." Excellent.

Now the children need to work like engineers to invent and design a sensor for the well.

Sofia says, "I'll use this bottle in my design to represent the well." And you can see a photo of this.

She's cut the top of the bottle to make a small tank.

Andeep notes, "We could use different conductors and insulators in our design to begin to find a solution to the problem." And in these pictures, you can see all sorts of things they could use as conductors and insulators in their design, including cardboard, bottle tops, coins, sponges, paperclips, corks, and even plastic pipes.

Let's check what we've learned so far.

In which career would professionals develop ideas to invent, design, and build objects that matter? Is it A, scientists; B, electricians; or C, engineers? That's right, it's C, engineers.

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

Now it's time for you to do more science.

You are going to design a system to detect water levels in a well.

So you're going to do the same thing as Andeep and Sofia.

Your design must include a circuit that has a switch which closes when the water level is high enough, and a bulb which lights up when the switch is closed.

There are a few things you need to do.

You should spend time discussing your ideas, decide how the switch will be triggered, and decide what will happen when the switch is triggered.

When you've had time to discuss your ideas, record your notes and sketches of your initial design.

Pause the video now and come back to me when you've done that.

How did you get on? What did you decide you would do for your design? Here is Sofia's design, and yours might be similar or it might be entirely different.

Every engineer works differently.

So Sofia has got a cork covered in foil as a sensor, and you can see that it floats on the water.

She's covered her cork in foil because the silver or kitchen foil is an electrical conductor.

So one end of the circuit is attached to the wire, which is attached to the cork, and the other end of the circuit is a wire which hangs down into the well.

So when the water level rises, the cork floats up, touches the hanging wire, and completes the circuit to turn the light on.

Sofia's done a good job with her design.

However, her teacher is worried that with this design, the circuit may get wet.

She's got a wire dangling in the tank, so that's something that Sofia might like to think about if she tries to improve her design later.

I wonder what imaginative ideas you came up with for your design.

Well, we're coming towards the end of our lesson, so let's look at the summary to remind ourselves what we have learned.

There are sensors all around us to detect changes in things like temperature, motion, moisture, light, and distance, among others.

Sensors are used in everyday appliances, such as washing machines, lights, burglar and fire alarms. Strict safety rules must be followed when planning to use electrical components near to water.

And engineers take ideas from paper and the lab to invent, design, and build things that matter.

Thank you for joining me for this lesson.

I've enjoyed learning about sensors together, and I hope that you have too.

I wonder if it's made you think about how the things you used every day were designed.

Well done for your hard work and have a great day.

See you next time.