Question 17 1AE01 - First Assistant Engineer

The Correct Answer is D **Explanation for D (electrical conductivity of water):** Salinity, which is the concentration of dissolved salts (ions) in water, directly determines how well the water can conduct electricity. When dissolved salts increase, the number of mobile charge carriers (ions) in the solution increases, leading to higher electrical conductivity. A salinity indicating system (or salinometer) measures this electrical conductivity. By establishing a relationship between the measured conductivity and known salinity values (often corrected for temperature), the system can accurately determine the water's salinity. **Why the other options are incorrect:** * **A) specific gravity of water:** Specific gravity (density relative to pure water) does increase with salinity, and older methods (like hydrometers) used this principle to estimate salinity. However, modern, automated salinity indicating systems rely on measuring electrical properties (conductivity) because it is faster, more precise, and easily automated, making specific gravity the outdated or indirect method for a sensor-based system. * **B) hydrogen ion concentration of water:** The hydrogen ion concentration ([H+]) determines the pH of the water. While pH is an important water quality parameter, it is related to acidity/alkalinity and is generally independent of the bulk salinity (total dissolved salt concentration). Therefore, measuring pH does not accurately indicate salinity. * **C) electrical inductance of water:** Electrical inductance is a property related to how an object resists changes in current flow, often associated with magnetic fields (like coils). While water has some electromagnetic properties, salinity measurement is fundamentally based on measuring the resistance or conductance of the solution to an electric current, not its inductive properties.