Скачать или смотреть Variable Resistance | Engish

We can all imagine that when current passes through a wire the larger the wire the more resistance it encounters and so the energy delivered to the load gets reduced. This is also called the transmission losses and are a big drain in our power distribution.
We can study this using this very simple and interesting setup. We need a 9V battery, a torch bulb, holder flexible wires, 100 turns of nichrome wire wound on a pvc pipe. Connect one end of battery to the bulb and another to the nichrome wire. Connect a wire to the other end of the bulb and leave the other end of this wire unconnected as shown. An now when you connect this unconnected end to nichrome wire very close to where it is connected to the battery the bulb lights up very brightly. If touch it at a distance the bulb glows dimly. When the touch it away from the battery connected end, much linger nichrome wire is part of the circuit and current passes through much larger wire. This increases the resistance and less voltage is delivered to the bulb so the bulb glow dimly.

If you connect the wire at very far end the voltage might be so small that the bulb will not even light up.
So you can see the resistance increases with the length of the wire as being observed by here by this girl. 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