Hello, my name's Dr.

De Mello and I'll be teaching you today's lesson on electricity.

Welcome to today's lesson from the unit, "Series Circuits." Today's lesson is about electrical current.

By the end of this lesson, you'll be able to describe how electrical current flows from one end of a battery through a circuit, which will contain components and background to the other end of the battery completing a full circuit.

So let's begin.

These are today's keywords.

First of all, we have battery.

This is the component that pushes the current around the circuit.

The next key word is charge.

These are the small things that flow around the circuit and we'll talk a lot about them.

The third key word is electron.

Electrons have charge and they're the things that flow in metal wire to give us electrical current.

And electric current is the last keyword.

This is the thing that flows.

It's a bit like a river that's flowing past you.

Be sure to look out for these keywords in the lesson.

Here, we have the definitions with the keywords.

If you'd like to look at them in detail, pause the video, have a look, and then restart when you're ready.

This lesson has two parts.

The first part that we'll start with is looking at, what is a battery? And the second part we're going to look at, what is current? So starting with, what is a battery? A battery has a plus or positive end.

You can see that marked on the left hand side in gold in this battery in a holder.

The other end is negative.

This is not normally marked on a battery.

All batteries have a plus and a minus, positive and negative end.

If you take some time to look at batteries, you'll only see the positive one marked.

With batteries like this one shown, the positive end also has a small protruding disc to help make better contact.

Let's try a check for understanding.

Which of these three batteries has a pole labelled with the correct sign? Pause the video, make a choice, and then come back to check your answer.

Welcome back.

If you chose B, well done.

That's the correct answer.

Batteries don't have the negative sign normally shown.

They normally mark only the plus sign.

Chemical reactions inside the battery make the terminals positive and negative.

There are two sets of chemicals normally in a battery that react to make the terminals positive and negative.

These terminals push charges around a circuit when one is connected to the battery.

Here are a range of batteries, different sorts of batteries used for different things.

To start off with, we have a power bank, the large rectangle at the top.

This is designed to charge up devices when you haven't got an electricity power supply available.

Next we have rechargeable batteries, the green and the silver ones.

They're in sizes AA and AAA.

We also have an alkaline AAA battery.

This one isn't rechargeable, but you can recycle it as you should.

On the bottom we have a torch battery.

Then we have a watch battery, which sometimes is called a button cell, and there's one in the middle of the picture if you look very carefully.

And finally, there's a camera battery.

You're likely to encounter all sorts of these batteries around you, just look out for them, and a nice thing to do is to check to see if you can see the positive terminal somewhere to even have the negative terminal shown.

Your mobile phone also has a large rechargeable battery.

In fact, that makes up the biggest part of its weight.

The phone cannot work if the battery does not push current through the various circuits.

Electric cars also have large batteries that need to be recharged regularly.

You'll see these around where you live and go to school.

Let's try a check for your understanding.

Which of these statements is true about batteries? A, all of them are rechargeable.

B, they can come in different shapes and sizes.

C, they use fossil fuels to generate electricity.

D, they have a positive, a negative, and also a neutral terminal.

Pause the video, make your choice and come back and check your answer.

Welcome back.

If you chose answer B, they come in different shapes and sizes, you're correct, really well done.

All batteries are not rechargeable so A is incorrect.

Some of them run out of the chemical energy that they store and then they need to be discarded, preferably recycled.

All batteries don't use fossil fuels to generate electricity, they rely on chemical reactions and they do have a positive and negative terminal, but not a neutral one.

So D is also wrong.

The simple battery can be made using two different metals, for example, zinc and copper, and these can be stuck in a lemon.

The acidic juice and the lemon allows the chemical reaction to take place between the zinc and the copper.

And in this example, you can see there's a small voltage from the two metals reacting.

Batteries should be connected so they're aligned in the same direction.

So you can see this battery over here.

It has a positive terminal on the left and a negative terminal on the right.

Another battery if it's going to be connected, should also have its positive terminal on the left and a negative terminal on the right, and a third battery would do the same.

The positive and negative terminals should match up, and here, we can see the different symbols for the batteries as well.

Another thing to note is all the batteries should be of the same type.

Let's check your understanding.

Which of these three symbols of three batteries is correctly connected together? Have a look, make a choice and then come back to check your answer.

Welcome back.

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

Answers B and C have at least one battery connected the wrong way around or part of the battery missing.

Here is a task, task A to practise what you've learned.

Some pupils are trying to light a lamp as brightly as possible.

They have a variety of batteries as we've shown over here.

Explain how the pupils could do this safely.

We'll assume that the lamp is rated enough to be able to cope with the batteries they choose.

Pause the video, write out your answer and then come back to check how you've done.

Welcome back.

The pupils could have sorted the batteries into each different type.

You shouldn't really mix different types of batteries.

They can pick the type that has the most batteries and then connect them end to end pointing in the same direction.

They can then connect them to the lamp and see how bright it is.

Finally, they can repeat the steps with each type of battery to see which set gives the brightest lamp.

If you manage to get some of those right, really well done.

That was quite a difficult task.

We're going to see what current is and how it flows around a circuit, so let's begin.

A battery pushes negative charges out of the negative terminal and pulls them into the positive terminal.

You can see the simulation over here where the battery is pulling in charges from the right and pushing them out on the left, and these charges are going round the circuit into the bulb, lighting it up and back all the way round.

We're using in this simulation a blue circle with a negative sign in it to represent a negative charge in the wire.

Again, this is a bit like a cartoon.

It's not really what electrical charges are like.

These charges in this case are called electrons.

It is electrons that flow in metals.

Let's check your understanding.

Which of these statements is true about a battery? Answer A, positive charges pulled into the negative terminal.

Answer B, negative charge is pulled into the negative terminal.

Answer C, negative charge is pushed out of the negative terminal.

And answer D, positive charge is pushed out of the negative terminal.

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

Welcome back.

If you chose answer C, you're correct.

Negative charge is pushed out of the negative terminal.

The answers were combinations designed to confuse.

Here is another check for understanding.

Which diagram most accurately shows the direction of current in this circuit when the lamp is lit? Look at the circuits, make a choice and then come back and we'll check your answer together.

Welcome back.

If you chose answer B, well done.

That's the correct version.

There's current coming out of one terminal of the battery, route to the lamp and then back into the other terminal.

Answers A and answers C are not complete or are inaccurate.

Answer A shows current only going in one direction but not returning to the battery.

Answer C shows current coming out of both terminals, that doesn't happen.

The charges that flow around the circuit are the electrons that are too small to see even with the best optical microscopes.

This is a representation of an atom.

These are the electrons.

The electrons are represented in this case as small blue circles.

In fact, they're much tinier.

You might also see this way of showing electrons in a metal.

The atoms are the copper coloured spheres and the electrons are the tiny blue circles or spheres.

The electrons can easily flow between the metal atoms making metals good conductors of electricity.

Let's check your understanding.

Which two statements about electrons are true? A, they're negative charges.

B, they're blue.

C, they're tiny.

D, they're only found in wires.

Pause the video, make your choice and then come back and we'll check your answers.

Welcome back.

If you chose they're negative charges and you chose that they're tiny, well done.

We've just used blue to represent them and they're not just found in wires, they're found everywhere, all around us.

Well done if you've got those right.

If a circuit is broken, then the electrons cannot flow across the gap.

You can see a gap in this simulation and the electrons are stationary.

They're not flowing.

Even though they're not moving, there are still electrons everywhere in the circuit.

They're in the battery, the wires and the bulb.

Let's check your understanding.

Where, in a broken circuit, are there no electrons available to flow? Is it A, the wires? B, the filament bulb? C, the battery or D, the gap? Pause the video, make a choice and then come back to check your answer.

Welcome back.

If you chose the gap, that was correct, well done.

The wires, the filament bulb and the battery all have electrons that can flow around the circuit.

A flow of chargers like in this wire, electrons, is called an electrical current.

It's a bit like the current of water in a river flowing across.

Let's check your understanding.

A teacher uses a model of a river to explain how current flows.

What does the model use to represent charge? Is it A, the water in the river? B, the speed of the river? Or C, the ripples on the water surface? Pause the video, make a choice and come back to check your answer.

Welcome back.

If you chose the water in the river to represent charge, that's correct.

The speed of the river and also the ripples on the water surface are more likely to be used to explain how the current flows.

When electrons leave a battery as shown in this simulation, the same number of electrons enter on the other side and for every electron that enters the bulb, another leaves.

The current in this circuit is the same, here, here, here, here, and also here.

It's the same everywhere in the circuit.

Let's check your understanding.

Which statement is correct when the lamp in this circuit is bright? We have the choices, A, the current is lower after passing through the lamp.

B, the current is higher at the negative side of the circuit.

C, the current in the battery is higher than in the lamp and D, the current in the battery lamp and wires is all the same.

Pause the video, read through these again.

Make a choice and then come back and we'll check your answers.

Welcome back.

If you chose D, the current in the battery, lamp and wires is the same, that's correct.

The current is the same everywhere in the circuit.

We have a simulation over here of current flowing in the circuit, lighting a bulb with a switch that's turned on and off.

When the switch is turned on, current flows and the bulb immediately lights.

When it's turned off, the bulb immediately goes off.

Even when the circuit is very long wires, the bulb lights and goes off immediately when switched on and off.

This is because the current is the same everywhere in the circuit and as soon as the switch is either turned on or off, the electrons can immediately start flowing, or stop flowing.

You'll notice this at home with the lights, when you flick the switch on and off, the lights will come on immediately and go off immediately as you flick the switch.

In this circuit, when the switch is closed, all three bulbs come on at the same time with the same brightness.

Again, this is because there are charges electrons everywhere in the wires and the filaments, and they start flowing immediately when the switch is closed or stopped when the switch is opened and the current that's lighting the bulbs is the same everywhere in the circuit, so they all light with the same brightness.

The individual electrons only move a few millimetres a second, but the bulbs all light up immediately.

Let's check your understanding.

The switch is closed in the circuit and the lamps light.

Which statement is true about how the three lamps light? A, lamp 1 light first.

B, they all light at the same time.

C, lamp 3 lights first and D, lamps 1, 3 light before lamp 2.

Pause the video, make your choice, and then come back and check.

Welcome back.

If you chose B, that's correct.

All the lamps will light at exactly the same time when the switch is closed.

Well done, we've reached the end of this section.

Let's do task B to practise what you've learned.

We have a circuit over here with a battery, two bulbs, a switch, and a third bulb connected in series.

The switch in the circuit is closed to turn the lamps on.

Describe how the bulbs light, including the timing and the brightness.

And then two, give explanations for why the bulbs light the way you described.

Pause the video now, write down your answers and come back to check your answers.

Welcome back.

You could have written the following, so describing how the bulbs light.

The bulbs will all light at the same time, and because the current is the same, they'll all have the same brightness.

And then part two, give explanations for why the bulbs light the way you described.

They all light at the same time because there are chargers electrons flowing throughout the wires.

The chargers all start moving together when the switch is closed.

The bulbs will each have the same brightness because the same current will flow in all of them.

If you got those right, that's really well done.

Those are quite difficult questions.

You've reached the end of this lesson, so let's summarise what we've learned.

A battery uses chemical reactions to make charge flow in a circuit.

It has positive and negative terminals.

The components in a circuit contain many negative charges called electrons.

These are too tiny to see, but we represent them in a model as blue circles.

When electrons flow in a circuit, it's called an electric current.

And finally, the current is the same all around the circuit and it causes all components to switch off and on at the same time.

You've now completed this lesson on electrical current.

Very well done, I hope to see you soon again.