Your elders might have cautioned you
 
against touching electrical appliances
 
through wet hands. They fear, you might get an
 
electric shock.
 
I'll be indicating that the water in
 
your hand may conduct electricity? If yes,
 
then do all liquids conduct electricity?
 
Let's find the answers to all these
 
questions in this lesson. Let's see if
 
some liquids conduct electricity.
 
Let's take the liquid lemon juice. Let's
 
try passing electricity through it using
 
a
 
tester. The tester has a battery, a bulb
 
and the wires of the tester are open. The
 
two open ends of the wire, we are dipping
 
it them in a beaker filled with lemon juice. Now,
 
one more thing you have to remember here is
 
that the two open ends of the wire which
 
are dipped in the lemon juice, they
 
should not be placed very close to each
 
other.
 
There should be a distance of atleast
 
one centimeter between them. If they are
 
very close to each other, there might not be
 
electricity conduction taking
 
place through the liquid instead there will be
 
electricity connection directly
 
through the wires. So, we have to keep
 
them at least one centimeter apart. Again
 
before starting with our activity, we
 
should test if the tester is working
 
properly or not. For that, the open ends
 
of the wires of the tester should be
 
connected and once they're connected and
 
if the bulb glows, that means our tester
 
is working perfectly ok. But then if the
 
bulb doesn't glow even after connecting
 
both the wires, that means there is some
 
problem with the tester. So, we should
 
check all the connections, are they lose
 
or are they proper. Now, once we check the
 
connections and they are fine and
 
still the bulb is not glowing, that means
 
there is some problem in the bulb.
 
So, we should replace the bulb. Now, if
 
everything is ok. Now, if the tester is
 
working properly, then we can come back
 
to our activity. Now, remember one thing.
 
If the liquids between the two ends of
 
the wires conducts electricity, then the
 
bulb will glow and if the bulb glows that
 
means this circuit becomes a complete
 
circuit. But if the liquid between the wires
 
does not conduct electricity, the bulb
 
wont glow. So, this will be known as an
 
incomplete circuit. Let's come back to
 
our experiment. Now, here you can see that
 
the circuit is closed but still the bulb
 
isn't glowing. There could be many reasons
 
behind the bulb not glowing. One obvious
 
reason is that, the liquid is not
 
conducting electricity. That means lemon
 
juice is not conducting electricity. That
 
is why the bulb isn't glowing. But there
 
could be one reason behind this. This
 
circuit might not be working properly
 
due to which the bulb is not glowing. But
 
in our case, we have already seen that the
 
circuit is working properly. We've
 
tested it before. There could be one more
 
possibility due to which the bulb does not
 
glow.
 
In some situations, even though the
 
liquid is passing electricity through it,
 
the bulb wont glow. For that, recall why
 
does the bulb glow when an electric supply
 
is passed through it? Because the
 
electric current heats up the filament of
 
the bulb and starts glowing. But in our
 
case, maybe the current passing through
 
the liquid is very weak due to which, it
 
is not being able to heat the filament
 
sufficiently and the bulb is not glowing.
 
So, for this we can do one thing. We
 
can replace the bulb with led. Led can
 
glow even when weak electric current passes
 
through it. You know why the current can be
 
weak?
 
Because certain materials do conduct
 
electricity but they cannot conduct
 
electricity as easily as a metal does. So,
 
in our case lemon juice might conduct
 
electricity.
 
Let's see. Do you see the LED glowing? Yes.
 
That means lemon juice is conducting
 
electricity but the current passing
 
through the circuit is weak due to which
 
the bulb dint glow but led did. But while
 
using LED, we have to remember one thing.
 
There are two wires attached to an LED. They
 
are called legs. One leg is longer than
 
the other. So, when you're connecting the
 
led to a circuit, you have to remember
 
that the longer leg should be connected
 
to the positive terminal of the battery
 
whereas the shorter end should be
 
connected to the negative terminal of
 
the battery. By far, we have made testers
 
to test whether a liquid conducts
 
electricity or not and we have seen that
 
when electricity is passing through the
 
tester,
 
how does it affect a bulb and how does
 
it affect an LED. But now, let us see what
 
are the effects of electric current on a
 
magnetic needle. We know that electric
 
current produces a magnetic effect. If we
 
keep a magnetic needle near an electrical
 
wire, it will show deflection even if the
 
current passing through the wire is weak.
 
Let's take a tray from the inside of a
 
discarded matchbox. Let's wrap an
 
electrical wire around the tray few
 
times. We will keep a compass needle
 
inside the tray. Now, let's connect one
 
end of the wire to one of the terminal
 
of the battery and let's leave the other end
 
of the wire free. Let's take one more
 
piece of wire and connect to the other
 
terminal of the battery and leave the
 
end of the wire free. Let's join the
 
free ends of the wire momentarily. Do you see
 
the deflection of the needle?
 
That means, there is electricity
 
passing through the circuit. That means
 
our tester is working properly.
 
Ok. Now, that we know that our tester is
 
working properly,
 
let's dip the free ends of the tester in
 
lemon juice and see whether it is
 
conducting electricity.
 
Yes. Lemon juice is conducting
 
electricity because the a needle is
 
showing deflection. That is lemon juice
 
is a good conductor of electricity.
 
Let's repeat the experiment with milk. Is the
 
needle showing deflection? No! That
 
means milk is poor conductor of electricity.
 
Honey. No deflection. That means again
 
honey is a poor conductor of
 
electricity. Tap water. We can see the
 
deflection, right? That means Tap water is
 
good conductor of electricity. Vinegar.
 
Deflection is seen again.
 
That means vinegar again is a good
 
conductor of electricity. Vegetable oil.
 
No deflection, that means vegetable oil is a
 
poor conductor of electricity.
 
Let me tell you an interesting fact
 
about water. Pure water does not
 
conduct electricity but tap water does.
 
Because there are impurities mixed in tap
 
water due to which it conducts
 
electricity.
 
Ok. Let's quickly see whatever we've seen
 
in this entire lesson. We've seen that
 
liquid do conduct electricity but not as
 
easily as metals. We've seen that some
 
liquids are good conductors of
 
electricity
 
while some are poor conductors and we've
 
also seen the effect of electric current
 
on a bulb, on a LED and on a
 
magnetic needle.
