The aim of this paper is to provide a way of teaching the factors that affect resistance using mechanical pencil leads and the brightness of the light given out by a light bulb connected to an electrical circuit. The resistance of a conductor is directly proportional to its length (L) and inversely proportional to its cross-sectional area (A). Additionally, the resistance depends on the type of conductor. Resistance R can be thus be expressed as R = ?L/A, where ? is the resistivity of the conductor.