das  Siemens

B2

Estimated CEFR level.

/ˈziːmɛns/

💡 What exactly is 'das Siemens'?

'Das Siemens' (symbol: S) is the SI unit of electrical conductance. Conductance is the reciprocal of electrical resistance (measured in Ohm, Ω). A material or component has a conductance of one Siemens if a current of one Ampere flows through it when a voltage of one Volt is applied (S = A/V = 1/Ω).

The unit was named after the German inventor and industrialist Werner von Siemens (1816–1892). Sometimes the unit Mho (Ohm written backwards) was used in the past, but it is now obsolete.

⚠️ Important: 'Das Siemens' as a unit of measurement is not the same as the company name 'Siemens' (Siemens AG), even though the unit is named after the company founder. The company name is usually used without an article or as 'die Siemens AG'.

🧐 Grammar: Das Siemens in Detail

'Das Siemens' is a noun of neuter gender (sächlich). As a unit of measurement, it is usually not declined (nicht dekliniert), especially when used with a number. The plural form is very rare and mostly identical to the singular if used at all ('die Siemens').

Declension (Singular)

Note: Declension is mostly used only when the word stands without a numerical value or unit context, which is rare.

Declension (Plural - rare)

Example Sentences (Beispielsätze)

1. Der Leitwert dieses Bauteils beträgt 5 Siemens.
   (The conductance of this component is 5 Siemens.)
2. Ein Siemens entspricht einem Ampere pro Volt.
   (One Siemens equals one Ampere per Volt.)
3. Die Einheit des elektrischen Leitwerts ist das Siemens.
   (The unit of electrical conductance is the Siemens.)

🛠️ Usage and Context

'Das Siemens' is mainly used in physics (Physik) and electrical engineering (Elektrotechnik) to describe the ability of a material or component to conduct electric current.

• Typical Usage: Specifying conductance values for resistors (Widerstände), cables (Kabel), solutions (in electrochemistry), or biological membranes.
• Context: Scientific publications (wissenschaftliche Publikationen), technical datasheets (technische Datenblätter), textbooks (Lehrbücher).
• Comparison: It is the direct reciprocal of the Ohm (Ω), the unit of resistance (Widerstand). High conductance (many Siemens) means low resistance (few Ohms) and vice versa.
• Prefixes: Metric prefixes like milli- (mS), micro- (µS), or nano- (nS) are often used, as one Siemens is a relatively large unit.

🧠 Mnemonics and Memory Aids

Article Mnemonic

Think of S as the Symbol for the unit. Many scientific units or concepts in German use 'das'. So, 'das' for the Symbol S → das Siemens.

Meaning Mnemonic

Siemens helps the current (Strom) to speed along – it measures how well it can flow (conductance)!

🔄 Synonyms and Related Terms

😄 A Little Joke

Fragt der Physiklehrer: "Was ist der Kehrwert von Ohm?"
Schüler: "Mho?"
Lehrer: "Gesundheit! Aber wir sagen heute Siemens."

Translation:
Physics teacher asks: "What is the reciprocal of Ohm?"
Student: "Mho?" (sounds like a sneeze in German)
Teacher: "Bless you! But nowadays we say Siemens."

📜 A Poem about das Siemens

Wo Ströme fließen, leicht und schnell,
da misst man klar und professionell,
wie gut der Leiter seine Pflicht
erfüllt im hellen Lampenlicht.
Nicht Ohm, das hemmt mit Widerstand,
nein, das Siemens, wohlbekannt,
als Maß der Leitung, groß und rein,
so soll der gute Leiter sein!

Translation:
Where currents flow, light and fast,
There one measures clearly, meant to last,
How well the conductor does its duty
In the bright lamplight's beauty.
Not Ohm, which hinders with resistance,
No, das Siemens, known from a distance,
As the measure of conductance, great and pure,
So should the good conductor endure!

❓ A Little Riddle

Ich bin der Kehrwert stolz und frei,
von dem, was Strom hemmt, eins, zwei, drei.
Mein Namensgeber war ein Mann,
der Technik einst viel Glanz gewann.
Mit 'S' als Zeichen steh ich da,
in Physik und Formel, wunderbar.

Was bin ich für 'ne Einheit bloß,
sachlich, wichtig, riesengroß?

Translation:
I am the reciprocal, proud and free,
Of what hinders current, one, two, three.
My namesake was a man,
Who once brought much brilliance to technology's plan.
With 'S' as my symbol, I stand there,
In physics and formulas, beyond compare.

What kind of unit am I, tell me true,
Neuter, important, and quite large too?

Answer: das Siemens

⚙️ Other Information

• Naming: Officially adopted by the General Conference on Weights and Measures (CGPM) in 1971.
• Werner von Siemens: Was not only the namesake of the unit but also a pioneer in electrical engineering and founder of the company Siemens & Halske (now Siemens AG). He improved the telegraph and developed the first practical electrical generator based on the dynamo-electric principle.
• Dimension: The dimension of the Siemens in the SI system is kg⁻¹⋅m⁻²⋅s³⋅A².