Final answer:
The ratio of a coil's inductive reactance to resistance is called the quality factor or Q factor, which indicates the efficiency of energy storage in the coil.
Step-by-step explanation:
The ratio of a coil's inductive reactance to resistance is referred to as the coil's quality factor or Q factor. Inductive reactance (XL) is the opposition that an inductor presents to the alternating current due to its inductance and is directly proportional to the frequency of the AC signal.
The formula for inductive reactance is XL = 2πfL, where 'f' is the frequency of the AC voltage source in hertz and 'L' is the inductance in henrys. The resistance (R) is the opposition that the coil presents to current flow due to its material and dimensions.
The quality factor is an important parameter because it describes how efficiently a coil stores energy; a higher Q factor indicates lower energy loss relative to the stored energy. The Q factor is especially significant in resonant circuits such as in radios and oscillators. It's a dimensionless parameter that provides a measure of a coil's performance at a given frequency.