Introduction to transducers and simple example of amplifying from microphone input to speaker output

A basic introduction to transducers is provided along with solving for the amplification required in a basic transducer between a microphone input and speaker output. Below is basically what's covered.

A transducer converts energy from one form to another
Or it is "a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa"

microphone amplification example
Sound to electric signal -- amplify electric signal – speaker (12 W, 8 Ohms) (like a computer speaker)
Input Voltage range from 0 to 250 mV -- amplify electric signal – speaker (max 10 V)
To amplify correctly, we need to multiply 0.25 * K = 10 V
So K = V_out/V_in = 10/0.25 = 40
Volage range from 0 to 250 mV -- amplify electric signal by 40 – speaker (max 10 V)
In this case, we'd call that amplification value K=40