L3 : Faraday's Experiment - Electromagnetic Induction, Physics, Class 12 Video Lecture

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electromagnetic induction part 3 is
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before going ahead with part 3 before I
start with the experiments on
electromagnetic induction let me tell
you a little story or small story on
electromagnetic induction as the name
suggests electro + magnetic + induction
so this lesson will talk about something
related to electricity + magnetism +
induction what is induction the in in
your normal English what does the term
induction literally means induction
means to in do something or to produce
something so that means something will
get produced under the effect of
electricity and magnetism so something
is related to between electricity
magnetism and production of something so
basically electromagnetic induction is
nothing but production of electric
current due to magnetic field in our
previous lesson what we'll be studying
while we were studying magnetism we
stand in that a current flowing through
a conductor is capable of producing
magnetic field right here we will study
that a magnetic field is capable of
producing current in a conductor so it
is just the reverse of what we studied
in the previous lesson right so
electromagnetic induction means
induction of current due to magnetic
field now now back there was a scientist
named Faraday who's performed a series
of experiments and based on the results
which we observe which we obtained from
his experiments he gave a law on
induction he was the one who told us or
who introduced that there is a
phenomenon of electromagnetic induction
which takes place in nature so first we
will study the experiments which he
performed one by one and we will see
what were his observation in each of the
experiments and based on the results of
his experiments he gave
is law of electromagnetic induction so
let us look at in the first experiment
which Faraday perform what he did he
took a coil here if you see you took a
coil and attached a galvanometer to it
now so there was no question of any
current flowing through this pipe
because there is no battery at all there
is no source of current here so from
there the current come to this pipe okay
so you just place the coil and attach
the galvanometer to it so that the
galvanometer can show whenever some
current is flowing through the wire
because whenever some current will flow
through this wire the galvanometer will
deflect right so he made this
arrangement and then he took a magnet
and he brought the magnet near the coil
now what you observed was that as the
magnet was moved towards the coil as the
magnet was moved towards the coil the
galvanometer showed deflection similarly
as the magnet was taken away from the
coil the galvanometer again showed
deflection but in the opposite direction
right so this was quite interesting for
him he felt that there is no source of
current in the circuit they from where
this current coming obviously the
current is related to the magnet because
when I am moving the magnet nearer the
deflection is in one direction when I am
taking the magnet away the deflection is
in the other direction
right and when I am not moving the
magnet at all there is no deflection
that means current is flowing through
the coil when the magnet is brought near
the coil current is flowing in the
opposite direction in the coil when the
magnet is taken away from the coil it
was also observed that if the magnet is
moved very fast
the faster we move the magnets the more
is the deflection in the galvanometer
that means if the magnet has moved very
fast that means more and more current
will flow in the quiet so the amount of
current which will flow through the coil
depends upon how fast we move the magnet
right he also observed that if we do not
move the magnet at all and if we move
this coil if we move this
and we keep the magnet at one place even
then the same effect was observed so
what was his conclusion he concluded
that the relative motion between magnet
and coil induced electric current in the
coil so that means because of a relative
motion between the magnet and the coil a
current was produced in the coil right
now he performed another experiment to
know more about it so now what did
father he do in his second experiment he
took the same coin which he took in the
previous experiment what he did he just
replaced the magnet with another coil if
you see here instead of the magnet he
took another coil which was connected to
a source of current which was connected
to a battery so what was his observation
this time now this time there is no
magnet right so he he found that even
though the magnet was replaced with the
coil even in this case when he moved the
coil near the magnet and near to the
this point his old setup again the
galvanometer showed the deflection so he
observed that the same phenomenon
happened even now when he replaced the
magnet with another coil so that means
the current flowing through one coil was
able to produce current in another point
that is what is happening here right so
here what is happening some current is
produced in this coil because that is
obvious because it has a source of
current it has a battery so this is a
closed circuit so current is flowing
through this pipe but when we are moving
the spoil closure to this coil because
of this current which is flowing in the
coil there is a current which is getting
induced in this way so what did you
observe from this from this he concluded
that relative motion between coils
induced current so not only relative
motion between a magnet and the coil
induced current also the relative motion
between two coils induced electric
current so now what it is he performed
another experiment he performed a third
experiment in that experiment what he
did he took the same setup again now
to another violent now I wanted to see
whether relative motion between the
magnet or between the two coils is an
essential criteria for induction of
current so what we did we took the same
set up he took the other coil and now
what he did he did not move any of them
both were stationary but he kept this
circuit switched off right now the Kasai
kit is an open circuit it is not
switched on therefore there is no
current flowing in the circuit this time
is observed as soon as he switched on
the circuit at that moment there was a
momentary deflection in the galvanometer
again when the circuit was switched on
for a long time
then again the galvanometer showed no
deflection that means current was
induced then the circuit was switched on
but after the circuit was kept switched
on continuously there was no current
induced again when the circuit was
switched off
there was a deflection in the
galvanometer in the opposite direction
and again when the circuit was switched
off for a long time there was no
deflection so this was a very important
observation which Faraday saw he saw
that the galvanometer showed moment in a
deflection only act those two instants
when the system was undergoing a change
for example in this case when I switched
it on when the circuit was switched on
only at that time there was an induced
current in my coil just for few
milliseconds then after that there was
no current and however after that there
is current flowing in this circuit but
still no current isn't used here again
when this is switched off so that means
there is a changed earlier current was
flowing now current is not free so only
for that small period of time of change
Dokka there was some induced current in
this setup so that means current was
induced momentarily only during the
period when the system was undergoing a
change so he concluded from this that
relative motion is not an absolute
requirement for inducing panic that
one thing that he'll observe and besides
that he also observed that the there was
an induced current there is an induced
current in a circuit only when there is
some change in the system like earlier
the system was switched off when you
switch it on that means there is some
change which the system is experiencing
that time there is an induced current
similarly I live the system was switched
off and when you switch it on there is a
change with the system is experiencing
so during that period of change there is
an induced current right now based on
these three experiments Faraday gave his
law he said that current thank you
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