Electrical Basics – Units

The most important variables are the current, the voltage and the resistance. Then there is the time. The current I is given in amperes [A], the voltage in volts [V] and the eponymous resistance R in ohms [Ω]. Other relevant variables are the electrical power P in watts [W] and the electrical work, the product of electrical power and time.

This is designated as W and is given in watt seconds [Ws]. The time t is measured and specified in milliseconds [ms]. In many older publications and controls, you will also find the time indication in periods [Per], which was common for a long time. One period corresponds to 20 ms and was the smallest unit of time in the AC systems that were mainly used in the past.