Answer:
This question appear incomplete
Step-by-step explanation:
This question appear incomplete. However, the significance/functions of the "instruments" mentioned (in the completed question) can be predicted since these "instruments" generally have specialized function.
A thermometer is used to determine the temperature of a substance or an object. The electric heater uses electricity to produce heat (which can be utilized for different purposes). The power supply is used to supply electricity for instruments/appliances that may require electricity to function.