Final answer:
It is false that a heating and air-conditioning technician can fully troubleshoot systems without voltage; electrical testing requires power. Option B is correct.
Step-by-step explanation:
The statement that a heating and air-conditioning service technician can usually troubleshoot heating and air-conditioning systems without voltage being supplied to the equipment is false. While certain checks can be made without power, such as inspecting physical components for damage or blockages, electrical testing to diagnose issues with controls, thermostats, sensors, or circuits requires a power supply.
Furthermore, the claim that high-voltage wires are insulated is false. High-voltage wires connected to metal-frame towers are held aloft by insulating connectors but are typically not insulated themselves because the air around them acts as an insulator and covering them with insulation would be impractical and expensive.
Regarding heat pumps, they do work by transferring energy from one environment to another. A heat pump can transfer energy by heat from a colder place to a warmer place with the help of external work (option C), contrary to option D, which wrongly states the direction of heat transfer.
This makes it a versatile device that can heat or cool a space, depending on the need. Option B is also correct, as it states that a heat pump uses work to transfer energy from a warmer environment to a colder environment, which applies when the heat pump is in cooling mode.
Lastly, when we talk about very well insulated homes in Northern Europe remaining warm even when residents are absent, the explanation could lie in the thermal mass which stores heat or the use of passive solar heating and other innovations that retain warmth.
Also, an explanation for refrigerators, air conditioners, and heat pumps being most cost-effective with a small difference between the high temperature (Th) and the outside temperature (To) is because the smaller the temperature difference, the more efficient the cycle, typically leading to a higher Coefficient of Performance (COP).