Volta worked on the electrophorus that makes a static electric charge in 1775. Volta also studied what we now call capacitance, developing separate means to study both electrical potential V and charge Q, and discovering that for a given object they are proportional. This may be called Volta's Law of Capacitance, and likely for this work the unit of electrical potential has been named the volt. Around 1791 he began to study "animal electricity". In this way he discovered Volta's Law of the electrochemical series, and the law that the electromotive force (emf formula_1) of a galvanic cell. In 1800, he invented the "voltaic pile", an early electric battery, which made a steady electric current. It is credited as the first electrochemical cell.