Gas Technician 2 (G2) License Practice Exam

The correct answer is the ambient temperature, as it directly influences the characteristics of a thermistor. A thermistor is a type of resistor that changes its resistance based on temperature variations. Specifically, thermistors can be classified into two types: negative temperature coefficient (NTC) and positive temperature coefficient (PTC). NTC thermistors decrease in resistance as temperature increases, while PTC thermistors increase in resistance with rising temperature.

When the ambient temperature changes, the resistance of the thermistor also changes, which allows it to accurately measure and respond to temperature fluctuations in the heating system. This property is crucial for thermostatic control, as it helps ensure that the heating system maintains a desired temperature by adjusting the operation of the heating elements based on the ambient conditions.

Other options relate to different aspects of a heating system but do not directly affect the intrinsic properties of a thermistor. For example, the type of gas used does not impact the thermistor's characteristics, as the thermistor is not sensitive to the fuel type but rather to the temperature. Similarly, control circuitry refers to the broader electrical components that manage system operations but does not change the fundamental response of the thermistor itself. Finally, the wattage of a connected device pertains to the power requirements rather