concept explained on transducers

hello friends
i think we forgotten about concept explaining threads
ok now i am giving about transducers i had just studied it now just in brief correct me if i am wrong anywhere

well............,
coming to transducers first we have to learn why we went to transducers
in many cases we have to convert one energy to another energy
let me explain with an example
we have a quantity let it be electronic we have to transfer it but electronic wave transfer gets losses in higher level so we can change it to electrical quantity and transfer it as we in case of measurement too we need these types of goods

now lets see the definition
transducers:The device which converts one form of energy to another energy
as we are more fond on electrical quantities we use mostly electrical transducers
it changed the meaning as
A device which converts any energy to electrical energy is known as transducers
there are many types of transducers like passive transducers and active transducers
here comes the separate definitions
passive transducers: The device which converts any energy to electrical energy with external source i.e..., with another supply
these consists of passive elements like inductors,capacitors,resisters etc...,
Active transducers: The device which converts any energy into electrical energy without any external supply
let me say some examples for these types of transducers
like piezo transducers,electromagnetic transducers etc......,
in between there are many types in them

hope i am clear here and the next continuation will be posted soon as another thread
if i am wrong anywhere please specify them
this thread is left to discuss types of transducers