Faraday established that an e.m.f. can be induced in a coil by changing the amount of magnetic flux `(phi)` linked with the coi. As `phi = Ba cos theta`, therefore, three methods of inducting e.m.f. are by changing magnetic field B or by changing area A or by changing relative orientation `theta` of the coil w.r.t. the magnetic field.
Read the above passage and answer the following question :
(i) Have you heard of a battery less flashlight ? How does it work?
(ii) Can you operate a typical cell phone from the hip movements of the person?
Whant do you know about gas-elcetric hybrid autos ?

Explanation

(i) Yes, a flashlight without a battery can give s light for a few minutes. It is based on EMI. On shaking the flashligth, its permanent internal magnet passes through a coil, inducing some current. Thus current is converted into d.c. and is used for charging a capacitor. The charged capacitor then sends current through light emitting diode (LED), which gives us light.
(ii) Yes, a backpack generator is used to convert the hip movements of the person into electricity and produce 5-7 watt of electric power to operate a typical call phone.
(iii) Gas electric hybrid autos are the latest innovations in the auto industry. The engine is made smaller than the convertional one. Through the sue of EMI, some energy is supplied to batteries and electric motor. The purpose behind is to get more mileage for every litre of petrol consumed. This would make the auto cost effective.