Question

___ is the range of voltage that must be(or can be) applied to household electrical appliances.

Answer 1

Operating voltage is the range of voltage that must be(or can be) applied to household electrical appliances. For example, a typical fan in our homes has 160VAC ~ 240VAC for a 220VAC fan(VAC = Volts alternating current).
‘Operating Voltage Range" indicates the minimum and maximum voltages at which the fan will operate. It should be noted that in most cases if you run a fan at lower than nominal voltage, the fan will slow down and if you run at a higher than nominal voltage the fan will speed up.