Hello scientists and welcome to this lesson on investigating voltage.

This is the do and review stage.

Our outcome today is to investigate and explain how voltage affects the brightness of a bulb in a circuit.

There are some key words to consider in this lesson.

The first is voltage, then brightness, now effect, then sell, and finally, lux.

Now, don't worry if you are not too sure what some of these words mean.

The definitions are on the screen for you now.

It may be that you might have some idea as to what some of them mean, or maybe you are not sure about lots of them, but that's okay because as we go through the lesson, the definitions will become clear.

If you need to, you can pause video here and have a read of the definitions and then continue when you've caught up.

The first part of this lesson is called Investigating how voltage affects bulb brightness.

Izzy and Jun here have been planning an investigation to find out about the effect of voltage on the brightness of a bulb.

The brightness of a bulb is the amount of light that it gives out.

Their investigation, will try to answer this inquiry question.

How does changing the voltage, affect the brightness of the bulb? Izzy plans to compare the brightness of the bulb in a circuit when she uses different numbers of cells.

So, using different numbers of cells, will create different voltages in the circuit.

She plans to observe the brightness of the bulb, using her eyes, and then she can decide whether it's dim, bright or very bright.

She needs to be careful about using her eyes to compare the different results here, because staring at bright objects for too long, could cause some damage to her eyes.

Thinking about this, can you think of any problems that she may find? Pause the video here and have a discussion.

Restart when you've done that.

I wonder what's other problems you've discussed? It might be that staring at bulbs is going to hurt her eyes after a while, or maybe she's not going to be able to tell the difference, between brightness, especially if her eyes are a bit dazzled, after staring at lights for too long.

Let's move on and find out more.

Well, Jun says, "Well, I don't think that you can measure brightness, "accurately using your eyes.

"What piece of equipment could we use?" Jun has a point here.

Izzy may not remember what she meant by bright or very bright.

It's not very specific or scientific.

So, pause a video here and have a think.

Is there a piece of equipment that we could use here to measure some brightness? Were you able to name the piece of equipment that we could use to measure some brightness? Well, ideally she's going to measure the brightness, using a light sensor and a data logger.

A light sensor will measure the brightness of light in a unit called lux.

Here you can see a picture of a light sensor on the top of a data logger.

Data loggers can tell you all sorts of information, about the environment that you are in.

It can tell you about the sound.

It can tell you about brightness and how warm or how cold it is, as well as lots of other different parts too.

Some light sensors are attached to data loggers and they can display and store the measurements, but other light sensors will come on apps on tablets or mobile phones and it's important to remember that if you are using different devices in this way, that some of them may give out different readings to the other, which is why it's a good idea to use a variety of different types of light sensors.

Jun is trying to measure the brightness of the light from the bulb using a light sensor app on a phone.

Now, here is Jun's experimental setup.

You can see he's holding his phone above the light there and he's got two blocks in this circuit.

One is for a bulb and the other one is for a cell.

There are wires then going in between.

Now, your circuit may look a little bit different to this.

You may be using some crocodile clips instead.

Jun says, "I think something is broken though, "the reading is always the same, "even when I can see the brightness changing." Jun is measuring the brightness of all of the light in the room, not just the light from the bulb here.

How can he make sure that he only measures the brightness of light from the bulb? Is there a way that he can do this? Pause a video and have a discussion? Restart when you've done that, Is there a way that junk can measure this accurately, without taking a light measurement for the whole room? I wonder what you discussed.

Maybe they need to build something that they can do their experiment inside or is there a simpler way? Let's move on and find out more.

Jun and Izzy write up their final plan.

They have written down some notes and they've drawn two diagrams, which is going to be on the next slide.

One is to build a circuit with a cell and a bulb in a bulb holder of course, and then connect some wires to it.

Two, put a cardboard tube over the bulb to block out all the lights from the room.

Ah, so that was their answer.

I wonder if you came up with anything similar to that.

The two here are going to place their bulb deep inside a tube so that no other light can get in.

Number three, place a light sensor at the top of the tube to measure the brightness of the bulb.

Four, add another cell to the circuit to increase the voltage and repeat steps two and three.

Five, continue adding cells one at a time and measuring the brightness, until you have five sets of results.

So, essentially here, Jun and Izzy are going to create their own little dark room using a cupboard tube.

That's going to help improve their results.

Here are their diagrams. Here's one circuit diagram, including the position of the cardboard tube.

You can see the bulb labelled there and the cell as well.

Here though is an experimental setup diagram that they've drawn as well.

There's the light sensor going on the top, a phone or tablet or data logger and then the cardboard tube going down to the bulb in the bulb holder.

Let's stop and think here.

How can you measure the brightness of the bulb? Is it using your eyes and your memory? Using a light sensor and a data logger or an app? The answer here is B, using a light sensor and a data logger or an app and it's important to note here that you can observe the brightness of a bulb, using your eyes, but you can't measure it.

If you're after some scientific results here, it's good to have a unit of measurements to compare against and in this case, we are measuring using, which of the following units is light measured in? Vaults, glows, or lux? Pause video and discuss.

The answer here is lux.

The units that light is measuring is lux.

So, here is task A.

You need to carry out your own plan to find out if voltage affects the brightness of a bulb, or you could use Izzy and Jun's investigation.

If you do decide to change the investigation little bit from what Izzy and Jun are doing, then make sure that you draw a diagram of the type of investigation that you're going to do, just to make sure that it's really clear.

There's a table of results here that you can use as well.

The number of cells being included, going down the side there, the voltage that they're going to measure and the brightness of the bulb that they'll measure using their data logger or their light sensor.

Have a go yourself setting up that task and finding out the data to fill in the table.

Best of luck.

Restart the video when you've done that.

So, how did you get on? Now your results may be similar to these, but don't forget they can be very different, depending on the type of bulb that you use and the type of voltage that you're sending through your circuit.

Here you can see the number of cells, increasing in value down the side.

The voltage is going up too, and you can also see the brightness of the bulb increasing, all the way from 26 to 2,200 lux.

Wow, that is a massive increase, isn't it? I wonder if you found some of the same.

So, have we answered our investigation question here? By looking at these results, I think it's clear to see that increasing the voltage that you send through a circuit can definitely increase the brightness of a bulb.

You just need to ensure that you are measuring using the correct units here.

In this case, we've used lux.

The final part of this lesson is called making bulbs brighter or dimmer.

Izzy and Jun's results are shown below.

Here you can see the number of cells increasing on the left side, the voltage increasing down the middle and the brightness of the bulb increasing down the right.

So, with this investigation data can you spots any patterns? Pause the video here and discuss.

Restart when you've done that.

Hopefully you've had a chance to look and discuss.

Have you noticed any patterns here? Do these numbers multiply in any way? Is there any logic to how they've increased? Let's move on and find out more.

The results here show that changing the voltage of cells and batteries can affect the brightness of a bulb in a simple circuit.

I can see it's increasing there.

We've already established that it definitely makes a bulb brighter.

The lowest voltage is here and this had the lowest brightness setting and here is the highest voltage and this had the highest brightness setting.

A lower voltage will lead to a dimmer bulb and a higher voltage leads to a brighter bulb.

However, a higher voltage is not always the best idea.

Different devices are designed to run on different voltages, so if the voltage is too high, it can damage them.

A voltage higher than the voltage of the bulb can cause bulbs to burn out or maybe even blow, because a lot of heat is generated.

And when we say that the bulb will blow, we mean that the tiny filament inside, that small amount of wire coiled up on the inside of the bulb will pop.

That means that it won't be able to transmit any more current.

This will then create a break in the circuit, causing the whole thing to turn off.

You may notice when you look at plugs or other devices that there is a different voltage written on each one.

Each specific device that you own, will need a different voltage.

If you put too much in, it won't work.

And if you put in too little, it also won't work.

The problem here though is that by putting in too much, you can cause your device to overheat and then of course it's not going to work anymore.

So, Jun presented his results in a table, but Izzy wrote hers down on a sticky note.

There's Jun's table and there's Izzy's note.

What are the advantages and disadvantages of each method here? Pause the video and discuss.

Restart when you've done that.

So, what are the advantages and disadvantages here? Well, the results of an investigation can be recorded in different ways.

It's completely up to you and how you record it.

Among other ways, results could be presented in tables or could be presented in spoken or written forms. Tables are ways of recording results in rows and columns.

They're really useful when we want to organise our results neatly, particularly if there is a lot of data to go through.

Jun's table is much easier to understand than Izzy's note.

Things are laid out in a specific order.

Scientists can also present their results in writing or verbally.

To present your results verbally, means that you say them out loud to other people and often scientists will show a table of data and then explain them verbally to others.

Here you can see a lecture theatre where lots of people have gathered to listen to the results of particular experiments and you can see some different data being displayed on the board.

So, Izzy decides to explain the results verbally.

Have a little look here at Jun's table of results.

What could she say? Pause a video and have a think.

Restart when you've done that.

So, what kind of things could Izzy say here? Our results show that the bulb in our circuit got brighter when the voltage increased.

When the voltage was 1.

5 volts, that's one cell.

The brightness of the bulb was 26 lux.

And when we added a second cell to have three volts, the brightness went up to 323 lux.

So, the brightness kept increasing every time we added a cell.

And when we had five cells or 7.

5 volts, it was 2,200 lux.

So, using all of that data and Izzy's explanation there, changing the blank of a cell could affect the brightness of a bulb in a simple circuit.

The answer here is voltage.

Changing the voltage of a cell can affect the brightness of a bulb in a simple circuit.

Stop and think again.

A lower voltage leads to a blank bulb.

What answer would you put here? Pause the video and think.

Restart when you've done that.

A lower voltage leads to a dimmer bulb.

What happens if the voltage supplied to a bulb is too high? Will it go dimmer? Will it burn out or will it get brighter? Pause the video and discuss.

Restart when you've done that.

So, what happens in the voltage supply to a bulb is too high? It will burn out.

So, here is your final task.

You need to plan a verbal explanation of your results and then present them to someone else.

Your plan will be a script noting the things that you say.

You need to think here and describe your findings and then end with a conclusion.

You need to try and include as many of the following words as you can.

Cell, battery, circuit, bulb, brighter or dimmer, voltage and push.

Have a think and use some of your best scientific explanation skills here to describe what has happened in your investigation.

Best of luck.

Restart the video when you've done that.

So, how did you get on? This is an example of something that you could have said.

Our results show that the bulb in our circuit got brighter when voltage increased.

When the voltage was 1.

5 volts when there was one cell, the brightness of the bulb was 26 lux.

When we added a second cell to have three volts, the brightness went up to 323 lux, and the brightness kept on increasing, every time we added a cell.

And when we had five cells or 7.

5 volts, it was 2,200 lux.

Can you notice here how the person who is given this written explanation hasn't written down every single result? They would probably have that displayed on the board behind them as they talk, but it's important to note, some of the key milestones in the project, usually the beginning and then the middle, and then the end.

So in conclusion, our results showed us that the increased push, provided by increased voltage, led to increased bulb brightness.

Your explanation may have been slightly different to this and that's okay because your results, could have been slightly different.

Whatever it is that you've written down to explain your results, I'm sure it will clarify the things that you have found in your investigation.

Well done.

So, let's summarise our learning.

Equipment such as a data logger can be used to record bulb brightness in lux.

Changing the voltage of cells and batteries can affect the brightness of a bulb in a simple circuit.

A lower voltage leads to a dimmer bulb and a higher voltage leads to a brighter bulb.

A higher voltage can cause a bulb to burn out or blow, due to excess heat generated.

The results of an investigation can be recorded in a table and presented using verbal and written forms. By completing this investigation, I hope that you've got a greater understanding of what you can do to a circuit.

So, increasing these cells, which will increase the voltage is going to generate more power.

But of course, you need to be careful there as you can cause sometimes irreversible damage to the devices that you use.

Even if it's not just a bulb, any device will need a particular amount of voltage sent into it.

So, any investigations that you do in the future, you now know that you'll need to check the type of voltage that the device is going to use, or otherwise you're going to end up with a device that you can't use anymore.

However you use the results of this investigation, I wish you all the best for your scientific investigations of the future.

Best of luck.

My name is Mr. Wilshire.

Thank you very much for listening.