Which unit is used to measure the relative voltage, current, or power of a signal?

The unit used to measure the relative voltage, current, or power of a signal is the decibel. The decibel is a logarithmic unit that expresses the ratio of one value of a power-like quantity to another. It is often used in telecommunications and audio applications to represent the strength or intensity of a signal.

For example, when measuring the power of a signal, the decibel scale provides a convenient way to express very large or very small ratios in a more manageable form. A change of even a few decibels can correspond to significant changes in signal strength, making it particularly useful for engineers in assessing performance and loss in various systems.

In contrast, while watt is a unit of power, it does not provide a relative measure. Similarly, the bel is a larger unit and is less commonly used than the decibel in practical applications, whereas amperes specifically measure electrical current and do not offer a method for comparing relative levels. Thus, the decibel stands out as the proper choice for measuring the relative aspects of voltage, current, or power in signals.