Question

How do amplifiers work without violating Law of Conservation of Energy?

(a) They amplify one factor of the input and reduce others

(b) They work on the law of conservation of mass

(c) They violate the Law of Conservation of Energy

(d) They amplify the signal by taking an input from an external source

The question was asked in an interview for internship.

This intriguing question originated from Active and Passive Devices in portion Diode Circuit of Analog Circuits

Answer 1

Correct option is (d) They amplify the signal by taking an input from an external source

To elaborate: The Law of Conservation of Energy is not violated because the additional power is supplied by an external source, usually a DC battery or equivalent. The amplifier neither creates nor destroys energy, but merely reshapes it into the waveform desired.