Capacitance-type electronic grain moisture meters determine the moisture content of grain bulk primarily based on the fact that:
Options:
(A) Liquid water has an exceptionally high relative dielectric constant ($\approx 80$) compared to dry grain starch and protein matrix ($\approx 3\text{--}5$).
(B) Water molecules have higher magnetic permeability than dry cereal husk.
(C) The electrical breakdown voltage of grain decreases linearly with protein content.
(D) Microwave photons induce nuclear magnetic resonance in bound hydrogen atoms.
Answer Key:
A
Step-by-Step Solution & Explanation
Capacitance moisture meters measure the capacitance $C = \varepsilon' \varepsilon_0 A / d$ of a cell packed with grain. Because liquid water has a huge dipole moment, its relative dielectric constant ($\varepsilon' \approx 80$ at room temperature) dwarfs that of dry grain starch and cellulose ($\varepsilon' \approx 3\text{--}5$). Therefore, small variations in moisture content produce large, measurable changes in total capacitance.