Definition
The SI unit of electrical conductance, equal to the reciprocal of one ohm. One siemens is the conductance of a circuit in which a potential difference of one volt produces a current of one ampere. Symbol: S.
Plain English
A unit that measures how easily electricity flows through something. The higher the siemens value, the easier the current passes. It is the opposite of resistance, which is measured in ohms.
Context Anchor
Seen in electrical theory, aircraft maintenance references, and some test equipment readings when checking how well a circuit or material conducts electricity.
Derivation
Named after Werner von Siemens (1816–1892), a German electrical engineer who made major contributions to early electrical and telegraph technology. The unit was officially adopted in 1971 to replace the older term 'mho' (which was 'ohm' spelled backward, signaling that it was the inverse of resistance).
Why Pilots Care
Pilots do not normally use siemens in the cockpit, but understanding the term helps when reading about aircraft electrical systems or discussing electrical checks with maintenance personnel.
Analogy
If ohms measure how much a wire resists the flow of electricity (like a narrow pipe), siemens measure how easily it lets electricity through (like a wide pipe). High siemens means easy flow; high ohms means hard flow.
Intuition Check
Do not read Siemens here as only a company name. In this context, it is a unit of measurement for how easily electricity flows.
Example Sentence 1
The conductance of the wire was rated at 0.5 siemens, meaning it offered very little resistance to current flow.
Example Sentence 2
Technicians use a meter calibrated in siemens to verify good connections in the aircraft's electrical bus.