Which of the following is NOT a characteristic of direct current measurements?

The correct choice identifies "Variation in voltage" as not being a characteristic of direct current measurements. Direct current (DC) is defined by its steady, unidirectional flow of electric charge. This constancy means that the voltage in a DC circuit typically remains constant over time, rather than varying.

In DC measurements, the voltage is stable and predictable, contributing to the constant flow of electricity and allowing for devices to operate without fluctuations in power. The characteristics of being polarity dependent refers to the fact that DC has a positive and a negative terminal, which is essential for the function of many electrical devices. Overall, the defining traits of DC emphasize its uniform nature, making the variation in voltage an inaccurate aspect concerning its measurements.