Why can a machine not be 100% efficient? (Please don't copy off the internet. I know when you do.)

Acoil formed by wrapping 80 turns of wire in the shape of a square is positioned in a magnetic field so that the normal to the plane of the coil makes an angle of 28.0° with the direction of the field. when the magnetic field is increased uniformly from 200 µt to 600 µt in 0.400 as, an emf of magnitude 80.0 mv is induced in the coil. what is the total length of the wire?

What is a carrier wave and how does it affect what you hear on the radio

How many times did thomas edison mess up the light bulb