Oersted Experiment - Moving Charges & Magnetism Video Lecture - Class 12

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make sure that you have watched the
previous video before going ahead with
this one so we will now study hosted
experiments what is it that he did that
made him conclude that electricity and
magnetism are so closely related to each
other basically what he did was he did
something not very complicated he did a
simple thing it a made it prepared or he
designed an electric circuit a very
simple circuit all he wanted was a wire
which conducts current here in this
circuit for today he took a wire
connected the bulk to it and a battery
to it so what happens when the bulk when
you switch it on then the bulb starts
blowing so that means when the bulb is
glowing your wire is conducting current
that means current is flowing through
this wire and when current is flowing
through the wire what he did he took a
magnetic compass or magnetic needle as I
told you he brought this magnetic needle
and I told you just now that what is the
purpose of this needle I mean I will
tell you about all those things that how
this needle function and why is it
always pointing towards one direction we
will discuss all those things in our
next lesson so as of now you should all
you should just know that magnetic
needle is a device or instrument which
will always point towards the south
direction it basically tells you the
direction right so what he observed was
when you break this magnetic needle in
front of the wire which is carrying
current the need shows some deflection
now when does this needle show
deflection since it is a magnetic needle
this needle will show deflection when
you bring it to some magnetic field
right so now here you are you didn't
bring it in front of a magnet like
normally what happens is when you bring
this needle in front of a magnet it is
showing deflection that is acceptable
because there is a magnet so there is a
magnetic field around the magnet but
here in this case he saw that there is
there was nothing
other than the current carrying wire so
when he brought the magnetic needle in
front of the wire
it showed deflection so then he extended
his experiment a bit what he did
he took the magnetic needle away from
the wire when he took the D this away
from the wire he saw that the deflection
reduced
similarly when he brought the needle
closer and closer to the wire the
deflection increased so he found out the
relation he with his observations and
the results he concluded something he
observed that the needle is not
deflecting randomly there is a
particular pattern of deflection of the
needle and what is that pattern he
observed that when you bring the Mac
vent when you bring the magnetic needle
in front of a wire which is cagin
current the needle shows deflection that
was one thing and also the direction in
which the needle is getting deflected
that direction is also specific so what
was that direction so what how he
observed to I mean how he reached this
result was that he performed a series of
experiment he placed the needle at many
different places and observed the result
and with his results he concluded that
the direction of deflection is nothing
but a tangent drawn to an imaginary
circle which is drawn taking this wire
as the center let us suppose if you
consider this wire as the centre you
imagine it in a separate figure let us
suppose if I say this is the wire this
is a wire which is going to ring so if
you imagine this wire as the centre and
then if you draw a circle I am sorry it
is not exactly a cycle but whatever if
you draw a circle then the tangent to
this circle gives the direction of
deflection of this magnetic needle that
was his observation right so that was
all that osted concluded he just
concluded that any wire which is
conducting current produces magnetic
effect right that means it produces
Bedingfield so that means electricity
has a close relation to magnetism and
you also observed that the direction of
the magnetic field was somewhat like
this was somewhat a tangent to a virtual
circle drawn taking the wire as the
center so this was what ørsted concluded
so he said that magnetic compass needle
deflected when current passes through a
wire deflection is along the tangent of
a virtual circle with wire as centered
and plane perpendicular to the wire so
that means this is the wire you take the
wire as the center and you draw a circle
in the plane perpendicular to the wire
so this is the plane which is
perpendicular to the wire so you draw a
circle like this
so tangent to this circle gives the
deflection of the magnetic needle right
so this basically gave us a final result
that charges and motion not only
constitutes current but it also gives
rise to magnetism so when charges are
moving it gives rise to magnetic field
as well so then later it was observed or
it was concluded somewhat like this that
if you have a conductor here this green
rod is nothing but a kind of conductor
or you can consider it as a conducting
wire so their current is flowing where
you can see that this shows that current
I is flowing through this conductor so
that means when current is flowing
through a conductor there is a magnetic
field around this conductor like how we
talk about electric field similarly you
have something called magnetic field but
the difference is that when I talk about
electric field I talk about charges
which are at rest if a charge is not or
even if it is not moving that charge
will have an electric field around
itself right so that when another
charged particle comes it experiences a
force because of that electric field
that you remember all those concepts
right there is a charge so that charge
will produce an electric field around
itself
now another charge
particle comes into the pen fairy
so that charged particles will
experience a force due to the electric
field produced by the first charge like
that is how it was in case of electric
field similarly in case of magnetic
field when charges are moving that means
when charges move what happens it
constitutes current so that means
current basically produces a magnetic
field that means again here also if some
other charged particle comes into the
periphery of this magnetic field then it
will experience some the magnetic field
it will experience a force due to the
magnetic field as well this doesn't mean
that this charge is not having an
electric field of its own that means
electric field is also charges produce
electric field as well as magnetic field
but charges at rest will produce only
electric field but charges in motion
will produce magnetic field as well so I
hope I am clear that how is electricity
and magnetism related to each other so
magnetism it is nothing new which was
born out of the world it was just that
the electricity itself produces
magnetism that means charges in motion
they accept produce magnetic field and
because of this magnetic field the
entire phenomenon of magnetism occurs so
the conclusion of ørsted experiment was
moving charges produce a magnetic field
in the surrounding region so I hope you
understood the analogy between electric
field and magnetic field like how you
how you understand the concept of
electric field in case of electrostatics
similarly you understand the concept of
magnetic field in magnetism right okay
so this is what it is the same figure
which I displayed in the previous slide
so now you clear that means when the
charges are moved in C I am repeating
this over and over again so that the
concepts are absolutely clear in your
mind I mean you don't need to memorize
things you should understand things the
charges when they are at rest Yuki
charge at rest okay so that charge will
produce an electric field around itself
so similarly when that charge starts
moving along with electric field it will
also produce a magnetic field then oh
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