What is the term for unwanted electrical signals induced into or superimposed onto a power or signal line?

The term for unwanted electrical signals that are induced into or superimposed onto a power or signal line is "Noise." In the context of electrical engineering and communication systems, noise refers to any unwanted disturbances that can distort or disrupt the intended signal. This can arise from various sources, including electromagnetic interference, thermal noise, and crosstalk from other signal lines.

Noise can affect the performance and reliability of communication systems by reducing the signal-to-noise ratio (SNR). When the noise level is high compared to the desired signal, it becomes difficult to discern the intended message, leading to errors in data transmission and reception.

While interference relates to similar concepts of unwanted signals, it is often associated with the deliberate or unintentional mixing of signals, such as from competing transmission frequencies. Static is a more colloquial term used to describe particular types of noise, usually in audio contexts, and signal loss refers to the reduction in power of a signal as it travels through a medium, which can occur for various reasons, including distance, attenuation, and indeed, noise itself. Therefore, "Noise" is the most precise term for the unwanted electrical signals in this context.