When the same power is delivered through wiring of the same resistance, by roughly what factor does the Joule loss in the wiring change if the supply voltage is raised from 12 V to 48 V?

Answer: A. 1/16×

Since power P = VI, for the same power, quadrupling the voltage reduces the current to 1/4. Wiring loss is I²R, so it becomes (1/4)² = 1/16. For example, delivering 2.4 kW requires 200 A at 12 V but 50 A at 48 V. 48 V systems are used in mild hybrids, electric auxiliaries and the like, allowing thinner, lighter wiring. Staying at or below 60 V is another advantage, since it does not require the rigorous electric-shock protection of high-voltage systems. 1/4× is the current ratio, not the loss ratio.