Hi.
My name is Melissa.
I'm a scientist here at Science North.
And I'm here to talk to you today
a little bit about electricity.
Now, what exactly is electricity?
Electricity is a force driven by electric charges.
Now, electric charges can come
in both positive and negative forms.
When we have charges that are flowing,
when we have charges
that are moving and powering electrical devices,
we say that we have current electricity.
One the other hand, when we have separate charges
that are at an imbalance, we call that static electricity.
Now, how does one create static electricity?
You probably had--
A few of you may have this idea.
It might be the easiest and most fun way
to create static electricity.
Now, another really interesting way
that we can detect static electricity
is by using water.
Now, water has molecules that are polar
so that means that although the molecule
is electrically neutral as a whole,
some parts of it may be slightly negative,
some parts of it may be slightly positive.
And essentially, that means that
we should get an attractive force between
the water and something that is charged with static electricity.
So, again, we need to make contact with materials
in order to generate static electricity
so I'm just going to make some contact
with this fur and PVC pipe.
Turn on a stream of water and hopefully
we'll get a chance to observe that attractive force.
Yes.
So, earlier, I mentioned that
charges come in both positive and negative forms.
Sometimes it can be difficult to know through static electricity
whether I've charged something positively or negatively
so what I want to do here is charge up this balloon.
So when I charge a balloon with fur,
I know that I get a negatively charged balloon.
Good contact and friction, transferring some charges.
Now I want to do the same thing to a second balloon.
Now, if I charge both balloons with like charges,
we know that likes repel
so I should be able to observe a repulsive force
in between these two balloons which they sort of do.
Well, I'll just let that go.
So if I were to now take this rod and this fur,
I'll be able to tell
whether I'm having an attractive force or a repulsive force.
It's going to tell me how this rod has been charged.
It seems like I'm getting
a little bit of an attractive force here,
closer to here where I charged the balloon earlier.
So this tells me if the balloon is a negative charge
then I've got a positive charged rod.
So I'm going to charge up this balloon one more time...
...and see what combination we get.
Now, when we rub two materials together,
it can be hard to tell
which one is going to become positively charged
and which one will become negatively charged, if at all.
All right?
Now, this has to do with
sort of an innate quality of different materials
as to what kind of charge,
whether they like to gain or lose electrons.
So, right here, I'm not seeing too great of a force.
Well, let's try to get a little bit more static
built up on here.
Now, this appears to be neutral.
So this combination of plastic and silk
doesn't generate enough static electricity
under these humid conditions to affect our balloon.
So I brought out a different electro-static device here.
It's an electro-static generator
and I've invited my friend Sarah over
so we can kick it into high voltage.
Thanks for coming.
So, Sarah has got a hand on top of the electro-static generator.
When I turn the machine on,
I'm going to get a belt that starts moving.
And just like I was charging things with friction earlier,
we're getting some friction that's happening
between the belts and the roller at the bottom of the machine
and another roller at the top of the machine.
So that's where our friction
and that's where our static electricity is coming from.
Now since Sarah has got a hand on top,
the charge imbalance
is going to transfer to her.
Now usually when we're talking about high voltage,
we're talking about a voltage level
that could be harmful to living things.
Now, this machine can generate static charges
up to about 300,000 volts but it's perfectly safe
because it can't generate a substantial current.
Now, this is also a really cool demonstration
of a static electric field
so we can see each one of Sarah's hairs
that are getting repelled
so there's a repulsive force between her head and her hair
and each one of her hairs.
So they're all trying to push away from each other.
Now, another interesting thing about static electricity
is that we always--
the charges want to move from an area of high potential
to an area of low potential like the ground
at any way possible.
The path of least resistance
kind of applies to static electricity.
So if Sarah were to bring her hand out,
I'm going to approach
and I'm going to give the electricity a path
to balance out that difference in potential.
And we can see the charges escaping from her head
through my body, down to the ground.
We can mostly just see them leaving her head.
The rest of the path is invisible.
Ooh, that was a good one.
Sorry about that.
That will be the last one.
That was, that was kind of mean,
but static electricity is a lot of fun.
And for the most part, it can be safe when worked with safely.
So other than static electricity,
we have what I referred to earlier as current electricity.
So, when we have electricity flowing in an electrical circuit
and powering an electrical device,
this is where we have current.
Now, in order to create a circuit,
we need to have a minimum of three things
in a simple circuit.
One of those will be a power supply, and in this case,
we've plugged into an outlet.
This could be a battery in some cases.
We also need conductors.
We need to be able to send the electricity
where we want it to go,
and we also need a load.
So here the load is going to be a light bulb.
Now, there are two main kinds of circuits
and one of them is called a series
and one of them is called a parallel.
And I want to do just a couple of demonstrations
with each of those.
Now, in a series circuit,
the components follow one after the other.
So, I've got the wires going to the first load
and then to the second and then back.
Now, the first thing to notice here is that
this light is dimmer than it was the first time
and this light is dimmer
than it would be if it were plugged in alone.
Now, I can add more components to this series circuit
and observe the same sort of thing.
And the lights are dimmer still.
So you can imagine,
adding more and more components into a series circuit
where the lights would be so dim
that they would barely even be on.
And that would actually be very impractical to wire
even one room in your house in a series.
So if you had one thing go out then they all would.
A series circuit is sort of like all or nothing.
And the best example of that are old Christmas tree lights
where one bulb would burn out and you had to check every bulb
in the whole string to find which one was burnt.
It would also be impractical if somebody turned off the light
in the bathroom while you were in the bedroom.
So, series circuits are not super practical on that end
so we have a different type of circuit
called a parallel circuit
that sort of helps us overcome these issues.
So I've got a couple of other components here
that I've wired to be in parallel.
Okay?
And what we should notice is
that each one of these lights is as bright as the other
and it is as bright as one alone
and I can show that here.
Another one of those advantages, if I take this light out,
this light can still stay on
and if I take this one out then you still have this one.
This is as bright as this one is going to go,
as bright as this one is going to go.
So using parallel circuits within our rooms,
within our homes,
makes just a lot more sense.