Which device is commonly used to amplify electrical signals?

The device commonly used to amplify electrical signals is the transistor. Transistors function as semiconductors that can control the flow of electrical current, allowing them to take a small input signal and produce a larger output signal. This property makes them essential in various electronic devices, including amplifiers, radios, and computers.

Transistors are based on the principle of current amplification, where a small current at the base (or gate, in FETs) can control a larger current flowing between the collector and emitter. This ability to increase the amplitude of signals allows for improved sound in audio devices, stronger signals in communication technologies, and clearer transmission in electronic circuits.

Other devices listed serve different functions: inductors are used to store energy in a magnetic field, generators convert mechanical energy to electrical energy, and transformers change voltage levels in AC circuits through electromagnetic induction. These functions do not involve amplifying signals in the same manner as transistors.