Can anybody tell me the simplest way to convert dc to ac using a circuit

 

Do you have any specifications that you would like to see as far as voltages, amperages, etc.? That would be a good starting point. Maybe tell us what you are trying to do?

 

Simplest? Buy a commercial inverter.

 

a relay wired as a buzzer is simplest, lowest arts count too.

 

A self-flashing LED could be used as a poor-man's oscillator.