"please help me understanding this":why a resistor(R) is used in series with the input in the shunt clipper circuit. . .and also how do we decide the value of R to be used in the clipper circuit is there any formula to find it???

 

A "shunt clipper" might be a diode or a zener diode. It limits the voltage but creates a huge current when the input voltage is higher than the threshold voltage that might burn out everything.
A series resistor feeding the shunt clipper limits the current. Simply use Ohm's Law to calculate the resistor value.

 

Thank u for the reply sir!!!!!

but i have one more doubt . . . why dont we connect a resistor in series with the input voltage in series clipper

 

What is a "series clipper"?
We were talking about a shunt clipper.

 

sorry for that sir >........
anyway i once again went through the answer u had given and understood the concept.
Thanks!!!!!