ElectricityIntroduction
It is the evening before Diwali, and Aman's family has hung three strings of fairy lights along the balcony. Two of them twinkle happily. The third is completely dark — all hundred bulbs of it. His uncle says that only one tiny bulb has gone bad, and that is enough to kill the whole string. Meanwhile, the tube light in the kitchen has just fused, and yet the fan, the fridge and the TV are all still running.
Why does one dead bulb black out a whole string, when one dead tube light does not black out the house? By the end of this chapter you will know exactly why.
Electricity has an important place in modern life. It is a controllable and convenient form of energy, used in homes, schools, hospitals and industries. Every appliance below runs on it, but each one is made for a different job. Sort them by what they are made to do.
Nine machines, one source of energy. In this chapter we ask the questions behind all of them. What is an electric current, and how does it flow round a circuit? What decides how much current flows? Why does a wire get warm when a current passes through it, and how is that heat put to use? And what exactly are the "units" on an electricity bill?