Source: http://web.a9lame.com/Documents/Lyc%C3%A9e/Bac%20FR/a-Tronc%20commun%20International/a-Tronc%20commun%20Science/b-Physique/b-Semestre%20II/b-La%20tension%20%C3%A9lectrique/a-Cours/Cours%207%20La%20tension%20%C3%A9lectrique.pdf