As you are no doubt aware, teaching electronics can raise many a tricky question! With this in mind,Electronics Educationaims to assist beleaguered teachers by offering some guidance with a series of ‘building block’ articles. In the first of our series of ‘Essential Ideas’ Torben Steeg explains the fundamentals of voltage, or, as it should be known ‘potential difference’.Look out for Part Two in the Summer issue of Electronics Education.