Hello, my name is Mrs. Mehrin, and I'm so excited to be learning with you today.

We are going to be learning all about variables in electric circuits and we are going to be doing an experiment today and reviewing it.

Let's begin.

Welcome to today's lesson from the unit, changing circuits.

Your lesson outcome today is I can investigate variables that may affect the brightness of a bulb in an electric circuit.

Now, I know that learning can sometimes be a little bit challenging, but that's okay because it just means that we are going to work really hard together, and learn lots of new things.

Now we are going to be touching upon some of your previous learning.

We are going to be using your planning from the lesson before this one if you also took part in that one.

Now here are your keywords for today.

You have four keywords.

Now you don't need to write these down because I am going to be addressing these, and referring back to them throughout today's lesson.

However, if it does help you to have them written down, you may pause the video now and do that, off you go.

Fantastic, well done.

And here are the definitions for those for keywords.

Again, you don't need to write these down 'cause I am going to be referring to them, but if you find that it does help you, you may pause the video now and jot these down.

Fantastic, well done.

Now, let's begin with the first part of our learning today, which is investigating how variables affect bulb brightness.

Now Alex and Laura have been building circuits.

They have made a sign for their classroom which has a light bulb on each corner.

And they want all of the bulbs on the sign to shine brighter, but they only have two cells.

Now they've been planning on an investigation to find out which variables affect the brightness of a bulb in a circuit.

Now what could their inquiry question be for that? I'll give you five seconds to think about your answer.

Off you go.

Fantastic, well done.

So Laura has come up with this suggestion, which variables affect the brightness of the bulb in a circuit? Now they've made a plan to investigate how each of these variables affects the brightness of the bulb.

So they've decided they're going to change the number of components and the position of components.

Now, is there anything else that they could change as well? Can you think of anything else that they might change in order to affect the brightness of the bulb in a circuit? I'll give you five seconds to think about your answer.

Off you go.

Fantastic, well done.

Now you may have said they might want to increase the number of cells, but they only have two to begin with, so they can't use any more cells in order to increase that brightness.

You may have said that they're going to increase the number of light bulbs they use.

Now this is their method.

They are going to build a circuit with a cell, a bulb in a bulb holder and connecting wires.

So they're going to make a really simple circuit here.

Then they're going to put a cardboard tube over the bulb in order to block out any light from the room and see whether or not that affects how bright the bulb is.

They're going to place a light sensor at the top of the tube to measure the brightness of the original bulb.

And then after they've done that, they're going to change one variable in the circuit.

So example, adding a bulb and repeating steps two and three.

So with steps two and three, they get to measure how bright that bulb was and then once they start changing those variables, they can continue to measure the brightness of the bulb and see whether or not it's been affected or not.

Now they're going to continue to change the variables one at a time until they've tested each of those variables in turn to see which one has actually helped.

Now the circuits they're going to build are shown in the table below.

Now if you took part in the previous lesson, then you may also have a plan that's similar to this.

So they decided that they were going to start with a basic circuits are nothing here where it says NA, not applicable, nothing here is going to be changing.

They're going to have the two cells which is all they have and the one bulb.

Then after that, they're going to put that tube over the light bulb, measure how bright the bulb is, and then they're going to move on to the first variable they're going to change, which is the number of bulbs.

So here now they're going to start using two bulbs with their two cells and then they're going to put the cardboard tube over the bulbs again, and see whether or not it's brighter or whether or not it's dimmer.

They're going to change the position of the bulb.

So they've decided to put it before the switch, then measure it and then after the switch, and again, measure it after that.

Now here we have a data logger, and it has a light sensor there and a light sensor measures the brightness of light in lux, lx.

Now Alex and Laura are going to use a light sensor attached to a data logger or an app to measure the brightness of the bulb.

So if you don't have a data logger, that's okay.

You can also find an app that will do that as well.

Now let's do a quick check-in of your learning so far, which of the following is the unit of brightness of a bulb is it A, flux, B, shine, or C, lux? I'll give you five seconds to think about your answer.

Off you go.

Fantastic, well done.

The answer is C, lux or lx.

Now, which of the following pieces of equipment could you use to measure the brightness of a light? Would you use an app on a tablet or a phone? B, a torch, C, a light sensor and datalogger, or D, a light reader? Again, I'll give you five seconds to think about your answer.

Off you go.

Fabulous, well done.

The answers are A, an app on a tablet or a phone, or C, a light sensor and a datalogger if you have them.

Now, here is your first task, you're going to either use Laura and Alex's method or you're going to carry out your plan from the previous lesson that you did to answer the inquiry questions.

So remember, if you didn't do the previous lesson, that's okay because you can still use Laura and Alex's method and you're going to answer the inquiry question which is which variables affect the brightness of a bulb? Now I want you to record your circuits, and your results in a table like you have before when you were doing the plan.

I'll give you some time now, I want you to pause the video here and I want you to have a go at doing the activity.

Off you go.

Fantastic, well done.

Now your results may look similar to this one here.

So we've got the basic circuit where nothing's been changed yet, and the lux, the bulb brightness here is 270.

Then they added two light bulbs and the bulb brightness was 48 lux.

Then they decided to change the position of that bulb.

So they went back to having just one bulb, but this time they had a switch as well and they put the bulb before the switch and that was 130 lux.

And then they put the bulb after the switch to see whether or not that had an effect and it was 128.

So have a look at your results now.

Are they similar? Are they different to what we can see here? Have you done your experiment accurately? If not, you can pause the video here and you can have another go.

Okay, off you go.

Fantastic, well done.

Fabulous, well done.

Now we are onto the second part of our learning, which is variables make bulbs brighter and dimmer.

So scientists use results from investigations to support, or reject scientific ideas and theories.

So Alex and Laura need to use their results.

So the one that's shown in the table here to answer their question which was which variables affect the brightness of a bulb? Now, I want you to think carefully about this question.

How will they use their results to know whether changing each variable did affect the brightness of the bulb? So what can they do and what can they have a look at in order to see whether or not changing those variables affected the brightness of the bulb? Now you can have a look at their results, you can have a look at your results and I want you to think carefully about that question.

So either you can pause the video here, or I'll give you five seconds to think about your answer.

Off you go.

Fabulous, well done.

So Alex and Laura need to compare the brightness of the bulb in two circuits to see whether or not each variable did actually have an effect.

So the first variable they considered was the number of components.

So in this instance, the component that they were going to change was going to be the number of the bulbs.

So I want you to have a look at Alex and Laura's results, and I want you to just think about what their results are showing you.

How has the bulb brightness been affected in these two circuits by changing a variable.

So I'll give you five seconds to think about your answer, but if you need longer you can pause the video here.

Off you go.

Fantastic, well done.

So we can see when they had the basic circuit here with two cells and one bulb, but the bulb brightness and lux was 270.

But as soon as they added those two bulbs in and they still had the two cells, so they didn't increase the number of cells.

Remember they're only changing one variable at a time.

Soon as they added that second bulb in, all of a sudden the bulb brightness went down to 48 lux, and now the teacher tells them about the effect of adding bulbs.

So the teacher says adding bulbs or other components is going to make the bulb dimmer.

Now, do their results support what the teacher's saying? So has adding those bulbs, or the components made this bulb dimmer? I'd like you to think about your answer, think about what we've discussed already.

Off you go.

Fantastic, well done.

So yes, they do but Alex says that he doesn't understand why the bulbs are getting dimmer because there's now two bulbs there.

So why are the bulbs getting dimmer and not getting brighter? Now I want you to think about that.

Why do you think the bulbs get dimmer when you're adding more bulbs to the circuit or adding more components to the circuit? Again, I'll give you five seconds to think about your answer, but if you need longer, you can pause the video and you can come back once you're ready.

Off you go.

Fabulous, well done.

So the teacher says when you are adding bulbs, it means that the voltage is equally shared among them all.

So voltage in those cells is having to be shared amongst more bulbs or more components now, and so therefore the bulbs are going to be dimmer.

So for example, if you use a two volt cell and you had one bulb, electricity is going to be pushed through that bulb at two volts.

So that one bulb is getting that two volts of electricity.

But as soon as you are adding another bulb, you are having to share it out.

So if you're sharing out those two volts between the two light bulbs, how many volts is there going to be for each of those light bulbs? I'll give you five seconds to think about your answer.

Fantastic, well done.

So there's only going to be one volt in each of those because you're dividing those two volts between two volts, so there's only going to be one volt across those two light bulbs, therefore making the light a lot dimmer.

Now the second variable that Alex and Laura tested out was investigating the position of where they put that bulb.

So they compared two new circuits, each one with a switch.

So here we had the position of the bulb, which was before the switch.

So you had two cells, one bulb and one switch, and in the second one the components were exactly the same, but the position of the bulb changed.

Now I want you to think really carefully, what do their results show you? What can you see here in terms of the bulb brightness and the variable that has been changed? So I'll give you five seconds to think about your answer.

If you need longer, you can pause the video and you can come back once you're ready, off you go.

Fantastic, well done.

So the teacher says a bulb will be the same brightness no matter where you place the components in a circuit.

Now, do their results support this theory that the teacher is saying, are the bulbs the same brightness wherever they place the components in a circuit? I'll give you some time now to think about that.

If you need to pause the video, you can, otherwise I'll give you five seconds.

Off you go.

Fantastic, well done.

So yes they do.

Now you might be thinking, but hold on a second.

The numbers are different here, one is lower than the other.

Yes, you are right.

One is lower than the other, but they're so close to each other that actually in this instance you'd consider them the same.

There's only two looks between them.

So in this instance, they would be considered the same amount of brightness.

Now, let's have a look at this question here.

It says, what is the effect on the brightness of existing bulbs, of adding extra bulbs to a circuit? Is it A, it depends on their positions.

B, they're going to get dimmer, or C, they are going to get brighter.

I'll give you five seconds to think about your answer.

Off you go.

Fantastic, well done.

The answer is B, they are going to get dimmer.

What is the effect on the brightness of existing bulbs of changing the position of the bulbs in a circuit? Is it A, the bulb may get dimmer? B, the bulb may get brighter or C, there's going to be no effect.

Again, I'll give you five seconds to think about your answer, off you go.

Fantastic, well done, the answer is C.

There's going to be no effect.

Now, here is the second part of your activity.

It says to look at the results from your investigation.

What do they tell you about which variables affect the brightness of a bulb? And I want you to write a conclusion which states whether or not your results support the following statements.

So number one, adding bulbs to a circuit means the bulbs will be dimmer because of voltage is equally shared between all of them.

So do your results support that statement? And number two, a bulb will be the same brightness no matter where you place it in a circuit, again, does your results support that statement? So I'd like you to pause the video here now, and I'd like you to have a go at that activity.

Off you go.

Your conclusion may be similar to this.

Now it should be similar to this.

So our results did support the theory that adding bulbs to a circuit means that bulbs will be dimmer because the voltage is equally shared between all of them.

When we had one bulb, the brightness was 240 lux, but with two bulbs it went down to 90 lux.

Our results also supported the theory that a bulb will be the same brightness wherever you put it in the circuit.

In our circuit with the switch, the brightness was 170 lux and in the second it was 179 lux which is quite close, which means that they can be said to be the same.

Now we are on to the summary of our learning today.

So equipment such as a light sensor and datalogger can be used to measure bulb brightness in lux.

Scientists use the results from investigations to support, or reject scientific ideas and theories and a bulb will be the same brightness wherever you place it in a circuit.

You have done fantastically.

I am so proud of your learning today.

You have done these experiments really well, and you've written some fantastic conclusions as well.

Great work.