The document is a physics investigatory project report on self-inductance completed by a student. It includes sections on the aim, apparatus, theory, circuit diagram, procedure, observations, result, precautions, and sources of error of the experiment. The experiment aims to study how the self-inductance of a coil depends on factors like the number of turns in the coil, geometry of the coil, and nature of the core material. The student observes changes in current and brightness of a bulb in an AC circuit when inserting an iron core into the coil and varying the frequency of the AC source.