Označeno: viri električne napetosti

Viri slikovnega gradiva: https://img.cdn-cnj.si/img/250/250/gf/gfnzFHJQpk6E https://www.sciencebox.eu/wp-content/uploads/2017/04/0046-upornik-1000ohm-4-e1533635023177.jpg https://img.cdn-cnj.si/img/250/250/VG/VGgGnyxxAb1e https://www.go-tel.si/instrukcije/images/galvanski-clen.png https://upload.wikimedia.org/wikipedia/commons/9/90/Solar_cell.png https://img.enaa.com/oddelki/mojDom/Assets/product_images/elektricni_kalorifer_iskra_fh01akt_iahnvd00061.JPG https://www.optimalna-energija.si/Data/Img/kako-deluje-elektricno-omrezje-M.jpg https://sl.wikipedia.org/wiki/Slika:Gorskii_04414u.jpg https://img.cdn-cnj.si/img/250/250/QR/QRreaMKGoJzh https://assetsemosproduction.vshcdn.net/content/images/product/default/31015.JPG https://www.superstrela.com/media/catalog/product/cache/9/thumbnail/600x/17f82f742ffe127f42dca9de82fb58b1/5/1/5199.jpg https://pushbikes.org.uk/sites/default/files/styles/large/public/IMG_0403%20%28Large%29.JPG?itok=QEUZlmEA https://ebatt.si/img/cms/liion%20baterije%20ebatt.jpg