Devices questions

Humidity is the measure of the amount of moisture in the air. A psychrometer is an example of a hygrometer. A psychrometer uses two thermometers to measure relative humidity; one measures the dry-bulb temperature and the other measures the wet-bulb temperature.

A stepper motor is used in devices that need precise positioning and speed control. Because it moves in precise repeatable steps, the stepper motor is used in devices like 3D printers, camera platforms, plotters, scanners, analog quartz watches. etc.

An articulator is a mechanical device used in dentistry. An articulator assists in the fabrication of removable prosthodontic appliances, fixed prosthodontic restorations and orthodontic appliances.

An opisometer, also called a curvimeter, meilograph, or map measurer, is an instrument for measuring the lengths of arbitrary curved lines. A simple opisometer consists of a toothed wheel of known circumference on a handle. The wheel is placed in contact with the curved line to be measured and run along its length. The instrument is most commonly used to measure the lengths of roads, rivers and other line features on maps.

During the early 1970s, two American chemists - M. Molina and S. Rowland - identified the theoretical threat of ozone depletion by the release of chlorofluorocarbons (used as a refrigerator coolant). Initially, the reaction was sceptical, but when in 1983 scientists discovered ozone hole, the abstract threat suddenly became real.