Final answer:
The component used to increase the size of a small physiologic signal is an amplifier, which is often made of transistors in electronic devices.
Step-by-step explanation:
The hardware component used to increase the size of the small physiologic signal is called an amplifier. Amplifiers are integral in various devices for enhancing audio, visual, or even biological signals. In the context of cellular phones, an amplifier is part of the circuitry that increases the sound signal before it reaches the earbuds, allowing you to hear calls and music. This circuit may consist of resistors, capacitors, diodes, and importantly, transistors, which are active components that primarily function to amplify signals.
Amplifiers are similar to the concept of resonance, as both involve the enhancement of an input signal or force to achieve a larger output without the need to apply a large initial force or signal.