Do motors run on an Ac source? If it does then do we need to convert ac into dc before supplying it to the motor?
There are both AC & DC motors available in the market. Ac motors run directly on the AC supply. The most commonly used ac motors are Single phase/3 Phase induction motors. If we have to use DC motor depending on the application and we have only Ac power supply we are required to convert ac voltage into appropriate Dc voltage required by the motor by means of rectifiers.
Most AC motors run on an AC source with no need to convert AC to DC. For control purposes, AC is sometimes converted from AC to DC then back to AC. There are also DC motors that use DC directly, but perform switching inside the machine that is something like converting DC to AC.
Motors come in both AC and DC varieties. They use different physical arrangements (e.g. DC commutator) and have different characteristics. There are plenty of references on the net e.g. http://www.ohioelectricmotors.com/2015/07/what-is-the-difference-between-an-ac-motor-and-a-dc-motor/#:~:text=A.C.%20motors%20are%20powered%20from,%2Dto%2DDC%20power%20converter.&text=A.C.%20induction%20motors%20do%20not,and%20have%20long%20life%20expectancies.
It is not necessary to convert AC to DC to drive an AC motor.
There are AC, DC and Universal (AC & DC) motors. AC motors are run on an AC supply, DC on a DC supply and Universal on AC or DC as required.
Here's the case of a universal series motor, run on AC for uni-directional operation and on AC converted to DC for bi-directional operation.