Hello, I'm Dr.

Demello and I'll be teaching you today's lesson.

In today's lesson we're going to learn how to use a circuit diagram to build a series circuit and also draw a circuit diagram from a completed circuit.

The key words in today's lesson are series circuit, which is a single loop circuit, which is the simplest sort of circuit you can get.

There's also circuit diagram, which will be drawing and showing you how to draw.

There are circuit symbols, which go in the circuit diagram, and there's standard symbols.

And then finally, there is complete circuit, which is important.

It's a circuit which has no gaps, which means electricity can flow.

Here are the keywords in definition form.

If you need to, pause the video now, have a look at them, and you can always come back and look at them later.

Look out for them in the lessons as they appear.

Today's lesson is going to consist of three parts.

We're gonna start off with, what is a series circuit? We'll move on to building a series circuit after that.

And then finally, we'll look at how you draw a series circuit.

So we'll start with, what is a series circuit? This series circuit contains three electrical components and some leads.

You can see that there's a battery with its attached symbol.

There are leads connecting everything together.

There's a switch which can be on or off.

There's a lamp which will light up when electricity flows, and that's connected back to the battery.

In terms of symbols, this is what that circuit would look like.

So you can see the battery at the top and then the switch and the lamp are at the bottom and they're connected by leads drawn with straight lines with no gaps.

So let's have a check.

Which of these is the correct symbol for a lamp? Have a look.

Pause the video so that you can make up your mind, make a choice, and then restart.

Okay, welcome back.

If you chose option B, that's the correct symbol for a lamp.

They're not drawn perfectly, but they are good enough.

A is not right because the line goes through the lamp.

It should not go through the lamp, there should be a gap.

And C is where someone has drawn the filament of a bulb rather than the crossed lines, which are the symbol.

There are some other components used in electrical circuits.

We have a motor and the symbol for a motor is an M inside a circle.

And notice there's no line going through the circle.

Our next symbol is a resistor.

You can see an image of a resistor and the symbol is a rectangle with the lines coming out of it to represent the wires.

Next up we have a voltmeter, which is a circle with a capital V in it.

And an ammeter is very similar, except it's got a capital A.

So a quick check.

Which component is represented by this symbol, a capital M inside a circle? You have a motor, a voltmeter, or a multimeter.

Pause the video, make your choice and come back.

Okay, welcome back.

If you chose the motor, well done, that's correct.

The voltmeter and the multimeter have different symbols, and the multimeter doesn't actually have a particular symbol.

A battery has a positive and a negative terminal.

The positive side is sometimes shown with a little plus, but it's the longer, thin line, the vertical longer, thin line.

And the negative side is the shorter, wide line.

Ammeters and voltmeters also have positive and negative terminals.

And you can see these pluses and the minus on the connections that go into the metre.

It's important that when you connect these components, you need to make sure they're the right way round.

And you'll find out how to do this in the circuits you make.

Circuit diagrams are used to show what a circuit is like and it's a simple version of a real circuit.

So here on the left we've got an image, a picture of a circuit, and here on the right is the equivalent circuit.

So the batteries are shown with the two batteries at the top.

The lamp is shown with the circle and a cross in it.

And then we have the switch, which in this case is a closed switch.

Here is a circuit that it's an image of a circuit or a picture of a circuit.

Which of these circuit diagrams are correct? Pause the video, make a choice, and then come back.

Okay, welcome back.

This one's a little bit of a tough one.

So if you chose circuit diagrams one, two, and three, choice D, that's the correct choice.

Circuit diagram one is actually the same sort of circuit, so is circuit diagram two, and so is circuit diagram three.

It's only four that isn't the same.

And if you look at four very carefully, you can see that the battery is oriented the wrong way around, everything else is the same.

So four is not the correct one.

So it's one, two, and three.

Well done if you got that right.

This is a series circuit which is complete.

There's only one complete loop and there are no junctions, so all the electricity flows around this single loop that's shown in purple.

Notice also that if you go through the components, there are no gaps.

In a series circuit, electricity passes through all of the components, one after the other.

Okay, so every component gets all the electricity.

And a circuit must be complete to allow electricity to flow.

If there's an open switch, electricity won't flow and it won't light, but pressing the switch, in this case, will complete the circuit and electricity will flow.

So let's test your understanding.

Which of the following shows a completed series circuit? Pause the video, make a choice, and then come back.

Okay, welcome back.

If you chose circuit A, well done, that's the correct circuit, you can see a single loop.

Circuit B has a loop for the left-hand bulb, but the right-hand one doesn't connect fully, so it won't light.

And circuit C has a gap, so that won't light.

So a completed circuit is circuit A and that one will work.

So here's a practise task.

There's a photo of a circuit.

List the components A to D shown in this circuit.

And then there's a circuit diagram that shows a possible circuit that matches the photo.

Is it correct? And if it's correct or it's not correct, explain your answer.

So pause the video now, write out your answers, and then come back to check them.

Okay, welcome back.

So listing the components, we have A is a battery, B is an ammeter, C is a lamp, and D is a motor.

And is the circuit diagram correct? Yes, the diagram is correct, the components are connected in the correct order and there's no gaps if you look carefully.

It doesn't matter if the components are not in the same positions as they are in the image, it's the order that they appear that's important.

And if you think about the photo of the circuit, you can move things around and the circuit will still work and it'll still be the same circuit, it'll just be the sequence or the order of the different components.

We're now going to do the next section, which is building a circuit.

So to build this circuit we're going to need three batteries, one switch, one ammeter, one lamp, one motor, and if you count the connecting leads, we'll need five leads.

So we start with our battery pack, and in this case it's a battery pack with four batteries.

We've picked this point to start because it's quite convenient, it's at the top, and then we're going to add the components in order.

So we add the switch with a lead and then we take the switch and connect it to an ammeter with another lead.

And the ammeter gets connected to a lamp and the lamp gets connected to a motor and the motor connects to the third battery.

Remember we only have three batteries in our circuit diagram, not four.

We have a choice of four, but we're choosing three.

We can then press the switch to light the bulb, and that's our circuit.

So when building a circuit, it's possible to start at any component, as long as the rest of them are added in the correct order.

So there's no reason why you couldn't start with the ammeter or the lamp and then work around in one direction, either clockwise or anti-clockwise.

The important thing is to get the circuit to match the order of the components.

The components in the circuit diagram can be in different positions.

So we have our original circuit diagram and we've got another version of the same circuit drawn slightly differently.

It's the order of the components that is really important.

So if you look you, if we started the battery with both of them, going clockwise, we next have the switch and then we have the ammeter followed by the lamp and then the motor before going back to the battery.

The sequence or the order is the same, so these two are the same circuits.

Let's have a check for understanding.

When building a circuit from a diagram, what is the method to use? Do you, A, start at any point and connect each component in order, ensuring none are missed, or B, always start at the battery and finish there, or C, the finished circuit should look exactly like the diagram? Pause the video, make your choice, and then come back.

Welcome back.

If you chose answer A, that's the correct answer.

Answer B is a possible way of doing it, but you don't have to start at the battery, you can start at any of the components, as long as you go in the correct order.

And in answer C, the circuit doesn't have to look exactly like the diagram.

They often look very different, so don't worry too much if they're not exactly the same.

Here's a practise task.

List the steps you would take to build the circuit shown below.

Write it out like you would a method, for example, and list all the different steps.

Pause the video, go ahead and do it, and then come back to check what you've written.

Okay, so welcome back.

You could have written something like this.

So count the number of components and wires that are in the circuit diagram and collect them.

This would be two batteries, three lamps, one switch, and five wires in this case.

Arrange the components in the order that they're shown in the diagram.

And then starting with any component, connect it to the next component with a wire.

Now, the battery is often a good place to start, but you don't have to start there.

And then repeat step three with each component in turn, checking that the circuit matches the diagram.

It's a good idea to check as you go along.

We're now on the third section of the lesson, drawing a circuit.

So circuit diagrams are drawn so that they're clear and easy to understand.

We use a simple set of rules when drawing them.

We represent components with circuit symbols.

We don't try and draw the components, we use accepted standard symbols.

We use straight and horizontal vertical lines.

And these lines are the wires drawn between components without any gaps.

And the battery or power supply is usually at the top, or the left, but you can start drawing the circuit at any point.

So when you're drawing a circuit diagram, you are going to need a sharp pencil, a rubber, and also a ruler.

So this is the way to draw a correct circuit diagram.

We're going to start with the two batteries.

So we have the symbols for the two batteries and we've added the leads.

So there's horizontal lines that go out from the two batteries and we've extended them downwards.

We can then extend one of them down and across to draw in the lamp.

And then we can finally fill in the switch.

The thing to note is the lines are straight and connected.

There is no gap between the lines and there's no gaps between the lines and the circuit symbols.

So we've used correct symbols, but they don't have to be perfect.

And we've got straight horizontal and vertical lines with no gaps between the components.

So this circuit diagram is being drawn with a pencil and it is acceptable.

You can see the batteries are not quite perfect, but they're pretty good, they're good enough.

And the bulb is not perfectly circular, but it's all right, okay? They are in the correct order, they're clear, and anyone can recognise that it's a circuit diagram.

Let's check your understanding.

Which of the circuit diagrams below is drawn correctly? Is it A, B, or C? Pause the video, make a choice, and then come back to check your answer.

Okay, welcome back.

If you chose circuit diagram C, well done, that's the correct circuit diagram.

A isn't correct because a line has been drawn through the bulb and the ammeter.

B looks almost perfect until you look at the second battery on the right and you can see it's not connected up to the lead.

So this circuit actually wouldn't work, so that's not drawn correctly.

Here is a practise task.

So there's a circuit diagram, it's not been drawn very well.

Label the errors in the circuit diagram and say what they are, and then draw a correct version of the diagram.

Pause the video, draw your diagram, and then come back to check your diagram against the answer.

Okay, welcome back.

These are the errors.

So starting at the top, the line drawn through the switch is not correct, that should have been left out.

The first lamp is fine, the second lamp has not been quite drawn correctly.

And then the lines were drawn curved rather than straight with a ruler.

So this is the correct version.

You can see there's three batteries at the top.

There's an open switch without the connecting line.

Two lamp symbols are correct and the motor is correct.

And the connecting leads all touch, so the circuit is complete.

Well done if you've got that right.

So you've completed the lesson.

Very well done.

We have, in learning about making a series circuit, covered the following.

Circuits are shown by circuit diagrams which use standard symbols to represent components.

There are some simple rules we use for drawing circuit diagrams so that they are clear and easy to understand.

A series circuit is an electric circuit with one complete path from one end of a battery all the way round to the other end.

Finally, when you are building circuits, it's important to follow rules so that you avoid making mistakes.

Well done for completing this video, and I hope to see you soon.