what is square law device? what is the function of this?

 Please suggest me any me hurry up!

i am wating your reply?

A square law device is something where either current or voltage depends on the square of the other quantity.!

For e.g: for a saturated MOSFET current(I) is directly prooportional to square of voltage(V²).

A diode characteristics also has a square but its not as clean.It's exponential and through a taylor series we get a linear, square ir cubic terms...

but anyway its useful bcoz it can b used as a modulator or mixer.

adding voltage is easy but multiplying them is hard..with a square law device like MOSFET it could b done easily.!

I proportional to(P.T) V²

I P.T (sin(w_ct) + m(t))²

I P.T (sin(w_ct))²  + m(t)² + m(t)sin(w_ct).

Now if we follow it with just bandpass filter on w_c we get simply m(t)sin(w_ct).

Amplitude modulation.