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Views: 2970 Description: DUBBED IN KANNADA by Mr. P. K. Nanavati. Motors, generators, transformers are all based on two fundamental properties of induction. Current flow through the wire produces a magnetic field and the changing magnetic field produces voltage across the wire of the conductor. For this induction apparatus you need 2 kg of insulated copper wire, some secondary wire, nails and ferrite magnets. The primary coil is made with 2kgs of insulated copper wire and will have about 3000 turns. Insert some cycle spokes, nails in the center to make core stronger. Scrape the ends of the wire and connect it to 220-volt AC mains. Remember to tape the joints to avoid an electrical shock. Now when you bring this coil near the nails they don't get attracted. But the moment you switch on the current, this coil becomes an electro-magnet and the iron nails are attracted towards it. Now see what happens when you insert an aluminum disc on top of this primary coil. The moment you switch on, the disc because of eddy currents becomes an electromagnet. If you put another disc on top of it that also becomes an electromagnet and starts to attract the previous disc. If you put four discs together and switch on, they become a strong electromagnet and try to fly out of the coil.
Take a secondary coil with about 100 turns and connect it to a bulb. As you bring the secondary coil closer to the primary coil the bulb lights up because of electrical induction. Amazing!
This demonstrates the concept of transformer. If you bring a coil with 200 turns the bulb will burn brighter than the 100 turns coil. This is because the voltage induced in the secondary coil is proportional to the number of turns. We have made another coil and connected bulbs at different tapping with different number of turns. Bulbs have been connected after 20, 40, 60 and 80 turns. On inserting this coil we can clearly see that more the number of turns the greater the brightness. This is a 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.
Finally we have a ferrite magnet connected to a spoke. 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. This work was supported by IUCAA and Tata Trust. This film was made by Ashok Rupner TATA Trust: Education is one of the key focus areas for Tata Trusts, aiming towards enabling access of quality education to the underprivileged population in India. To facilitate quality in teaching and learning of Science education through workshops, capacity building and resource creation, Tata Trusts have been supporting Muktangan Vigyan Shodhika (MVS), IUCAA's Children’s Science Centre, since inception. To know more about other initiatives of Tata Trusts, please visit www.tatatrusts.org....