Purpose: The aim of this study is to investigate the knowledge of prospective physics teachers on capacitors and electric field lines. Sample: The study group consists of 45 prospective physics teachers, 31 of whom are female, 14 of whom are male, studying at a state University in Turkey. Design and methods: A descriptive model was selected as the method of the research. The data of the study were collected through a measurement tool and semi-structured interviews prepared by the research. The measurement tool consists of open-ended questions and drawings. The answers received from the prospective teachers were subject to descriptive analysis. Results: The findings showed that prospective teachers had sufficient knowledge of the definition, function, and structure of the capacitor. However, it was determined that there were difficulties in understanding the source of the loads in the capacitor plates. Furthermore, although they knew the definition and structure of dielectric, their knowledge of the function of dielectrics was not based on a scientific basis. The prospective teachers were unable to establish a connection between the dielectric and the electric field. They have also been found to confuse electric field lines with electric current and magnetic field lines. The prospective teachers often drew point charges for the electric fields between the capacitor plates. It has also been found that they think electric field lines are real.