Which device is used to operate a radio when there is no current?what is used to get electric power in cars ?

Question

Which device is used to operate a radio when there is no current?what is used to get electric power in cars ?

Answer 1

I think you are asking "Which type of device is used to operate a radio when there is no battery?".  

It is possible to build an AM radio with a diode and no battery.  The diode extracts the energy from the radio signal to power a small earpiece.  Alternatively, buy a more conventional radio with a wind-up generator in it!

In the car.. it is again the generator that converts mechanical energy into electrical energy.

Answer 2

I don't understand the first question but perhaps the first answer is helping you out.

Electric power in cars is stored in lead acid batteries which are recharged from the alternator (the aforementioned generator), which is driven by a belt connected to either the crankshaft or another component which is connected to the crankshaft.