Contact Series

An arrangement or tabulation of substances in pairs, each intermediate substance appearing in two pairs, as the last member of the first, and first member of the succeeding pair, with the statement of the potential difference due to their contact, the positively electrified substance coming first. The following table of some contact potentials is due to Ayrton and Perry: CONTACT SERIES. Difference of Potential in Volts. Zinc--Lead .210 Lead--Tin .069 Tin--Iron .313 Iron--Copper .146 Copper--Platinum .238 Platinum-Carbon  .113 The sum of these differences is 1.089, which is the contact potential between zinc and carbon. Volta's Law refers to this and states that-- substances is equal to the sum of the differences of potentials between the intervening substances in the contact series. It is to be remarked that the law should no longer be restricted to or stated only for metals. 148   STANDARD ELECTRICAL DICTIONARY.