By what name is Voltage magnification of electromagnetism known?

The voltage magnification of an electromagnetic system, particularly in the context of resonant circuits or components (like inductors and capacitors), is often associated with the term 'Quality Factor', also known as the Q factor.

In the context of resonant circuits, the Q factor can also be interpreted as the ratio of the reactive power (which is maximum at resonance) to the active power in the circuit. When referring to a coil (inductor) in such a circuit, the Q factor of the coil, which is determined by the ratio of its inductive reactance to resistance, tells how well it can establish a voltage across its terminals that is larger than the voltage applied to it -- thus, one might consider the Q factor as an indicator of 'voltage magnification'

 Additional Information

The quality factor is defined as the ratio of the maximum energy stored to maximum energy dissipated in a cycle

\(Q = 2\pi \frac{{Maximum\;energy\;stored}}{{Total\;energy\;lost\;per\;period}}\)

\(Q = \frac{Resonant ~frequency}{Bandwidth}\)

In a parallel RLC, 

Bandwidth = \(\frac{1}{RC}\)

Resonant frequency = \(\frac{1}{\sqrt {LC}}\)

The quality factor of the parallel RLC circuit is given as:

\(Q=\frac{RC}{\sqrt{LC}}\)

\(\)\(Q = R\sqrt \frac{C}{L}\)