Hello, my name's Dr.

de Mello and I'll be teaching you today's lesson.

Today's lesson is about making parallel circuits and it comes from the resistance and parallel circuits unit.

The outcome we have is I can use circuit diagrams to build parallel circuits and draw circuit diagrams of parallel circuits.

Let's look at today's keywords.

The first pair of keywords are series circuit.

This is when you have an electrical circuit with one complete loop that goes from one end of the battery round to the other end of the battery.

There aren't any junctions.

It's one complete loop that you can trace around from one end of the battery to the other.

The next pair are complete circuit.

An electric circuit with no gaps in it is a complete circuit, so electricity is able to flow all around the circuit.

Then we have parallel circuit.

Now this is a circuit with more than one complete loop from one end of the battery round to the other end.

You'll also see that there are junctions in this circuit where the other loops branch off.

Finally, we have circuit diagram and this is a simple and clear way of showing the setup and components in an electrical circuit.

This lesson on making parallel circuits has three parts.

The first part is about parallel circuits.

Then we look at building parallel circuits, and lastly, in the third part we look at how we draw parallel circuit diagrams. So let's start with parallel circuits.

This is a series circuit.

There is only one complete loop from one end of the battery round to the other end.

There are no junctions in the loop.

Let's do a check for understanding.

Which of the following statements about a series circuit are correct? A, there is a single loop.

B, there are no junctions, and C, the loop starts and ends at the same point of the battery.

Pause the video now, make a choice and then come back to see how you've done.

Welcome back.

If you chose, there is a single loop that's correct.

If you also chose, there are no junctions.

That's also correct.

Well done if you got those right.

This is a parallel circuit.

There is more than one loop from the battery.

There's the first loop like before, and then there's the second loop which branches off, but it's also a single loop that goes around from the battery.

In this parallel circuit, there is a junction where the current can split into the two loops.

There is also another junction where the current from the two loops joins up.

These two circuits work in the same way.

They're effectively the same circuit, so let's see how this is the case.

There's a junction in both the circuits on the left where the current splits, and then there's another junction on the right where the current joins up.

Even though they look different, these two circuits are exactly the same.

Let's do a check for understanding which of the following statements about current at a junction are correct.

The choices are A, at a junction, current can split.

B, at a junction, current goes through only one loop.

C, at a junction, current can join up.

Pause the video now, make your choices and then come back to check your answers.

Welcome back.

If you chose A, at a junction, current can split.

That's correct.

If you also chose C, at a junction, current can join up.

That's also correct.

Answer B was incorrect at a junction, the current doesn't only go through one loop.

It'll go through both loops.

Well done if you got that right.

These two circuits can be shown with circuit diagrams, so looking at the one on the left, we've got two branches at the bottom and a circuit diagram would look like this.

So we have the battery at the top with the open switch, and then we've got two bulbs below it.

The circuit on the right can be shown by this circuit diagram.

This time, the battery and the switch are in the middle and the bulbs are either side of the battery, one above and one at the bottom.

These are both the same circuit.

They both have junctions on the left and they both have junctions on the right.

Each bulb is lit by a separate loop, so the first bulb had this loop and the second bob had this loop.

Again, even though they're in different positions, they're the same circuit.

Let's do a check for understanding which one of the circuits shown is different from the others.

There's a choice of A, B, or C.

Pause the video now.

Study the circuit diagrams carefully checking where the loops go, and then make a choice.

After that, come back and see how you've done.

Welcome back.

If you chose circuit A, that's different from the other two.

The other two are exactly the same circuit as we've seen before.

Well done if you got that right.

Recapping what we've done in parallel circuits, it's where the junctions are that is important.

These circuits are the same even though the components are in different places.

Here is a check for understanding.

Which of the following is most important when trying to determine if parallel circuits are the same.

Is it A, the positions of components? B, the positions of junctions or C, the positions of wires.

Pause the video now, make a choice and then come back to see how you've done.

Welcome back.

If you chose the positions of junctions.

That's correct.

Well done.

The positions of components and the positions of wires can vary.

The circuits may look very different even though they're the same.

Well done if you've got that right.

We've come to the end of the section.

Here's a task for you to practise what you've learned.

There are four circuits, A, B, C, and D.

Identify which of the circuits work the same way, and then explain your answer.

Pause the video now.

Go ahead, examine the circuits and write out your explanations and then come back to see how you've done.

Welcome back.

Circuits A, C and D are the same parallel circuits as they have junctions leading to two separate loops.

The two loops in each circuit each have one lamp, so they're the same.

Therefore, circuits A, C and D will work the same way even though the lamps and wire positions are different.

Circuit B is a series circuit which is different from the others.

Well done if you've got some of those statements right.

We are now going to do the second section, building parallel circuits.

When building a parallel circuit, it's best to follow a set of steps.

First of all, you collect the equipment needed, so in this circuit we need a battery, we need a switch, and we need two bulks.

You'll also need some leads to connect all the components together.

Here's a quick check for understanding which of the circuit symbols below represent a lamp.

Is it A, B, or C? Pause the video now make your choice and then come back to check how you've done.

Welcome back if you chose symbol A.

That's correct, well done.

To build a circuit, you first identify a single loop in the circuit and then starting at one point in the loop, it doesn't actually matter where you start as long as you start at one point, connect up the components one by one going in the same direction until that loop is complete.

In this circuit, we'll build the first loop.

We're going to start with the battery.

We'll connect that up to the bulb and then connect that up to the switch and then connect that up to the battery.

That's our first loop.

We then find the first junction on the first loop, and that's where we'll be connecting the second loop on the diagram, so we connect up the components starting with the junction and the wire and the next bulb and the wire to connect up that loop so we have the second loop.

It's also possible to start with the lower loop first.

Here's the lower loop.

We start with the battery again and connect up the wire that goes all the way around the bottom to the bulb, and that goes all the way back up to the top to the switch, and then that connects to the battery.

We then add the loop that has the bulb in the middle, connect up the wire, add the bulb, and connect up the other wire.

This is our first loop that we started with before, but this time we've called it the second loop.

It doesn't really matter so long as the junctions are in the correct place.

You can start building at any point in the circuit as long as each loop is completed in turn.

You could start at the battery or the switch or a lamp or the other lamp as long as you complete the loops in sequence, ensuring the complete, you'll build the correct circuit.

Here's a check for understanding which of the following steps must you do when building a parallel circuit.

The choices are A, start of the battery.

B, complete each loop.

C, always go clockwise.

Pause the video now make a choice and then come back to check your answer.

Welcome back.

If you chose complete each loop, that's the correct answer.

You don't have to start at the battery, you can start at any component as long as you follow a logical sequence and you don't have to always go clockwise.

You could go anti-clockwise, you'll still build the circuit correctly.

Well done if you got that right.

We finished this section and here's a chance for you to practise what you've learned.

You're going to build the following circuits, one, two, and three, using the circuit diagrams below.

Pause the video now.

Build each circuit in turn and then check how you've done.

Welcome back.

These are possible correct circuits.

There are other possibilities, especially if you use slightly different components, but try and see following each loop round, whether you've got the same sorts of circuits.

Well done if you've got something similar.

We've now reached the third part of the lesson drawing parallel circuit diagrams. When drawing the circuits, again, it's best to look out for junctions and loops, so here's our first loop with two junctions on either side, and then here's second loop coming off those junctions.

You start by drawing the first loop.

Again, it's best to go round in order drawing each component correctly.

You can then add the second loop.

Again, double check by following the circuit round from each junction.

Circuit diagrams should be drawn one loop at a time.

Correct symbols should be used, so double check them.

Horizontal and vertical lines for wires should be drawn with a ruler.

And finally, make sure there are no tiny gaps in the lines, especially at junctions and corners.

Let's do a check for understanding.

Identify the errors in the circuit diagram shown.

The possible errors are, A, the battery is the wrong way round.

B, there is a tiny gap in the middle branch, and C, there's a wire drawn through the ammeter.

Pause the video now, make choices and then come back to see how you've done.

Welcome back.

If you chose B, there's a tiny gap in the middle branch.

That's correct, and if you chose C, there is a wire drawn through the ammeter, making it the incorrect symbol.

That's correct as well.

Well done if you've got that right.

Now we have the final task to practise what you've learned.

You're going to draw the circuit diagrams for the circuits below, examine the circuits carefully and remember the rules for drawing circuit diagrams. Pause the video now and once you've drawn your circuit diagrams, come back and see how you've done.

Welcome back.

Your diagrams should look similar to these diagrams over here.

You may have some slight differences, but remember to check them.

Go around each loop in turn counting off the different components, and you should be able to see whether you've drawn similar diagrams. Well done if you've got these right.

We've reached the end of the lesson.

Let's summarise what we've covered.

A parallel circuit is a circuit with more than one complete loop from one end of a battery round to the other end.

Junctions in a parallel circuit lead into additional loops.

When building a circuit, a parallel circuit, it's best to build each loop one at a time.

Looking out for where the junctions are.

The same parallel circuit can look very different 'cause the components can be in different places, but the sequence of connections to components is what is important, and when you're drawing parallel circuits, use the loops and junctions.

You've done really well to complete this lesson.

I hope to see you again soon.