Working principle of inverter I got project on the working of inverter from school. I know this that DC inverter has an alternator switch which constantly changes its direction so that magnetic field is produced in primary coil due to which current is induced in secondary coil and we get output AC. So according to all this Electromagnetic induction should be the working principle behind the working of DC inverter. But DC can't take part in EMI, I know alternator is being used but it doesn't feels right. I hope I am right till this point I am taking following image as reference:

Please don't get mad at me if I got everything wrong.
 A: You are right. The alternator turns the DC of the battery into AC, which allows for changing magnetic fields in the primary. A transformer need a changing magnetic flux (which is why "DC doesn't work") - the alternating switch keeps changing the direction of the current, so the flux keeps changing. This induces e.m.f. in the secondary, and the result is an AC voltage on the output of the circuit.
The voltage wave form on the primary will be a square wave: the output waveform will be more complicated, depending on details of the resistance of the coils and the load. Obviously, the higher the switching frequency, the more regular the shape of the output: at very low frequencies, the output will "decay" between switching of the input alternator. 
A: Low-cost inverters like you see in a car work in this fashion. Ones used in power production, and higher-quality ones used in cars, improve the output by not switching 120 times a second (or 100 if you're in Europe), but many thousands of times. The output is sent into circuits that boost the voltage, sometimes without a transformer at all, and filter the output with capacitors. The result is a very accurate sine wave that is good enough to put on the grid.
