Final answer:
The ratio of a coil's inductive reactance to resistance (XL/R) is referred to as the coil's quality factor or Q factor, which measures the sharpness of coil resonance and energy loss.
Step-by-step explanation:
The ratio of a coil's inductive reactance to resistance (XL/R) is referred to as the coil's quality factor or Q factor.
The inductive reactance (XL) of a coil is the opposition to a change in current, which varies directly with the frequency of the alternating current (AC). It is given by the formula XL = 2πfL, where f is the frequency, and L is the inductance. The greater the frequency or the inductance, the higher the inductive reactance. Resistance (R) in this context is the ohmic resistance of the coil, which hinders the current flow due to the material's intrinsic property.
Inductive reactance has the unit of ohms, thus the ratio XL/R is dimensionless. This ratio, known as the Q factor, is a measure of the sharpness of the resonance of the coil or its selectivity, and it also signifies the energy loss related to the coil's reactance and resistance. A higher Q factor means lower energy loss and a sharper resonance peak.