It is well known that concept of electric field and electric potential and relation between them are one of the hardest to grasp at secondary level and even at university level. We propose a simple experiment using light emitting diodes (LED) that can be used at various levels to elucidate these concepts and demonstrate their behaviour.
The experiment can be considered as an example of "multilayered simple experiments" that the authors introduced at GIREP 2009 conference [1]. Some details of the proposed experiments represent interesting problems on their own.
Suggestions how to treat such problems theoretically and to compare the results with real experiments are presented.