Tip:
Highlight text to annotate it
X
we see so many electrical devices in our lives these days, motors, generators, transformers
and all of them are based on two fundamental properties of induction. a current through
the wire produces magnetic field and the changing magnetic field produces voltage across the
wire of the conductor. using this amazing experiment you can see both these properties
and see very counter-intuitive things as converting non-ferric or aluminium disc into a magnet.
for this you need the induction apparatus which is 2 kgs of insulated copper wire, some
secondary wire, nails and ferrite magnets. this is how you make the primary coil with
2kgs of insulated copper wire of about 3000 turns. in the middle of the coil you insert
some metal, iron rods, nails to make it a strong core. strong core concentrates the
magnetic field inside the primary coil and hence makes the effect 100s of times stronger.
scrape the ends of the wire and connect it to the power source. we should remember to
put tape so that you do not get a shock doing this experiment. this should be connected
to an AC power source. now when you hold this coil o the needles they don't attract. but
the moment you switch on the current, this coil produces a magnetic field and the iron
needles are attracted towards this magnet. this magnet does not attract the aluminium
discs. now see what happens when you insert it on top of this primary coil. the moment
you switch on, the disc becomes an electromagnet. this is because the eddy currents are produced
inside this aluminium disc and they make it a magnet. if you put another disc on top of
it that also becomes an electromagnet and starts to attract the previous disc. this
is independent of which side you put the disc on. if you put four of them together and switch
on they become a strong electromagnet with such a force that they fly out of the coil.
take a secondary coil with about 100 turns and connect it to a bulb. now see what happens
the moment you take the secondary coil and bring it closer to the primary coil. amazing!
this demonstrates the concept of transformer. see the moment you put this coil nearer to
the primary core there is current induced because changing magnetic field induces voltage
and there is a changing magnetic field because an AC current is passing through the primary
coil. this is the coil of about 200 turns. notice the brightness of the bulb. this is
much brighter then 100 turns. as the voltage induced in the secondary coil is proportional
to the number of turns. we have made this another coil and connected the bulbs at different
turns. at 20 turns we have connected a bulb, after 40, after 60 and after 80. now when
we insert this close to the primary coil, see you can clearly see how the number of
turns effect the brightness or the voltage generated or voltage induced in the secondary
coil. beautiful demonstration of electromagnetic induction. we have wrapped these nails together
and we will see the effect of the strong core. if you bring the coil with 100 turns , see
how dimly the bulb is lighting. the moment we put this core inside the secondary coil
the effect is 100 of times larger, because the magnetic field is concentrated now. now
we have a small coil with about 1000 turns and we have connected an LED to it. the moment
we bring this coil close to the primary coil, again the LED starts to glow, because there
is voltage induced in this coil. now here we have a ferrite magnet connected to a spoke.
see the magnet attracts the nail. now the moment we bring this magnet close to the primary
coil and switch on the current, the magnet starts to rotate. this is the basic concept
of an AC motor where the electromagnetic field produced by the primary coil interacts with
the magnet and makes it rotate. see how children are having fun with induction.