The freshness of fish can be measured by placing a fish between the plates of a capacitor and measuring the capacitance. How does this work? (?Hint: ?As time passes, the fish dries out. See Table 24.1.)

Solution 15DQ The capacitance of any capacitor depends on three factors area of the plates, the distance between the plates and the dielectric constant of the space in which it is kept . To have an idea about the freshness of the fish, take a capacitor and measure its capacitance. Now, place a fish between its plates. As the time passes the fish dries out or loses its moisture, and the value of dielectric constant will change. Since all other parameters are constants, we can conclude that the capacitance will be related only to the dielectric constant which is in turn depends on the freshness of the fish. Hence, by knowing the kinetics of losing moisture (zero order, first order, second order ) we can easily relate the freshness of the fish to the measured capacitance value.