|A) mercury thermometers||B) alcohol thermometers|
|C) platinum resistance thermometers||D) thermoelectric thermometers|
The resistance of metallic conductors e.g, platinum, increases with rise of temperature . The increase in temperature results in a decrease of current which can be recorded in a galvanometer if the conductor is included in an electrical circuit. Thus the temperature can be known; platinum resistance thermometer is used generally for accurate scientific work. When two dissimilar metals are joined at the ends, and these ends are subjected to a difference of temperature, a current flows through the metals. Greater the difference of temperature , greater the current. So the curent strength can form the basis for measuring the difference in temperature. And when one of these temperatures is known, we can calculate the other.