Nicholas Callan and experimental philosophy under Dr. Cornelius Denvir. He introduced the experimental method into his teaching, and had an interest in electricity and magnetism. Callan was ordained a priest in 1823 and went to Rome to study at Sapienza University, obtaining a doctorate in divinity in 1826. While in Rome he became acquainted with the work of the pioneers in electricity such as Luigi Galvani (1737–1798) who was a pioneer in modern obstetrics and Alessandro Volta (1745–1827) who is known especially for the development of the electric battery. In 1826, Callan returned to Maynooth as the new Professor of Natural Philosophy
Volta potential by its work function, and so dissimilar metals can show an electric potential difference even at equilibrium. The Volta potential is "not" an intrinsic property of the two bulk metals under consideration, but rather is determined by work function differences between the metals' surfaces. Just like the work function, the Volta potential depends sensitively on surface state, contamination, and so on. The potential is given by the formula: formula_1, where V is the potential, The Volta potential can be significant (of order 1 volt) but it cannot be measured directly by an ordinary voltmeter. A voltmeter does not measure vacuum