The difference in electrical charge between two points in a circuit, expressed in volts, is best described by which of the following?

The best description of the difference in electrical charge between two points in a circuit, expressed in volts, is accurately associated with the concept of a thermistor. A thermistor is a type of temperature sensor that operates based on the principle of resistance changes in response to temperature variations, thus involving electrical characteristics relevant to voltage differences.

The relationship between voltage and resistance is essential for understanding how a thermistor can be used in circuits to measure temperature, as changes in temperature will affect the resistance, leading to corresponding changes in voltage. This underpins the very basic principle of how electric circuits convey different physical properties.

Considering the other options, plethysmography, pressure transducers, and pneumotachometers operate based on different principles and are used to measure parameters such as blood volume changes, pressure variations, and airflow respectively. They do not directly relate to the concept of electric voltage in a circuit as thermistors do, making thermistors the most appropriate choice for describing the electrical charge difference in volts.