How does an alternator charge a battery

How is the battery charged when the car is started

The alternator converts mechanical energy that is generated by the engine into electrical energy that is used to charge the battery and to power the vehicle's electronic devices

An alternator that works like a generator, it uses rotational force to generate energy, it is attached to the engine pulleys by a belt, so as the engine starts running, it also runs then it sends the generated power to the battery for a charge.it has a stator coil, a rotor and a diode

(Alternator and a generator are not the same thing but achieve a mass of the same goal)

The battery supplies current to charging system when the engine is stationary, the battery is being charged by the alternator when the engine is running

How will you know if the car alternator is working/functional?

Check your dashboard after you have started the engine if the battery light is still on or off if on this tells you that the battery is not charging, for that matter it means that the alternator doesn't work. Or your fanbelt it maybe slacks or not tight, if the engine is started the warning lamp is off during this the alternator is charging or working.

When you start the car and remove the battery terminal and if the car goes off that means the alternator has a problem

you can use a digital multimeter to test battery voltage when a vehicle is started you will get voltage around 13.5 volt

you can bring a metal close to the alternator while running you feel the metal been attracted like a magnet

what has required RPM of the alternator to power for 12v DC?

RPM is related to Hz. 1500rpm for 50Hz and 1800rpm for 60Hz