Final answer:
The use of grounding in modern cable systems represents a significant safety improvement over the older knob-and-tube wiring by including a ground wire, which prevents electrical shocks and allows circuit breakers to function properly when faults occur.
Step-by-step explanation:
An important improvement from knob-and-tube wiring to modern cable systems is the use of grounding. The three-wire system utilized in modern wiring includes a live/hot wire, a neutral, and an earth/ground wire. This configuration enhances safety by ensuring the neutral wire and the case of an appliance are grounded, establishing a low-resistance path directly to ground. It prevents electrical shock hazards by keeping the case at zero volts and allows the circuit breaker to trip if there is any issue such as a wire's insulation wearing off and contacting the case. Unlike the older two-wire systems that lacked an earth/ground wire, the three-wire system also includes other features such as circuit breakers and ground fault circuit interrupters (GFCI) to guard against thermal overload and unintended current paths, thus preventing potential fires and electrical shocks.