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.
