In which wire in an A. C. housing circuit is the switch introduced to operate the lights ?
The switch is introduced in the live wire.
Consider the implication of placing a switch or fuse in the neutral wire of an appliance. If the switch were open, or the fuse blown, no current would flow through the load. However, the entire load circuit would still remain elevated to a lethal voltage with respect to neutral and ground, posing a shock hazard. In such an instance, the appliance may give the appearance of being de- energized, while in reality, it presents an opportunity for electrocution.