Final answer:
Transformers are used to change voltages from one value to another. In heating or cooling systems, they provide the low-voltage power source for the control circuit.
Step-by-step explanation:
Transformers are devices that change voltages from one value to another. They are commonly used in heating or cooling systems, where they provide the low-voltage power source for the control circuit. In a power distribution system, transformers are also used to step down high voltages to lower values before being introduced into homes for safety reasons.