First Assistant Engineer · 1AE01 · Engine · Fresh Water and Instrumentation · CURRENT-Q511-Q0017
Salinity Indication: Why Conductivity Matters
Relate dissolved ions to electrical conductivity and a shipboard salinity indication.
A salinity indicating system functions on the basic principle of measuring the __________.
- A. specific gravity of water
- B. hydrogen ion concentration of water
- C. electrical inductance of water
- D. electrical conductivity of water
Correct answer: D. electrical conductivity of water
Why this answer is correct
The salinity indicating system measures electrical conductivity because dissolved salts increase the water's ability to conduct current.
Governing principle
Ions from dissolved salts carry electrical current, so conductivity provides an indirect measure of salinity.
Reasoning
- Dissolved salt separates into charged ions.
- Those ions increase electrical conduction through the sample.
- The instrument relates measured conductivity to salinity.
Why the other choices do not fit
A. Specific gravity can be used in other concentration measurements but is not the basic principle of the electrical salinity indicator.
B. Hydrogen ion concentration is pH.
C. Inductance is not the water property measured by the salinity cell.
Related lesson
RO Pretreatment, Salinometer Conductivity and Extended Shutdown
Flashcard preview
What electrical property is commonly used to indicate salinity?
Electrical-conductivity measurement is a common basis for marine salinity indication because dissolved ionic salts increase water conductivity.
Sources
- U.S. Navy training material · Fireman · Chapter 11, electrical salinity indicating cells
- USCG National Maritime Center · Q511 General Subjects I · Question 17 and official answer key
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