Comparing the observed spectrum with known spectra allows one to determine the composition of the material emitting the incident light. Resistors A resistor acts as a restriction to the flow of electric current, much as a reducing valve acts as a restriction to the flow of water in pipes. The amount of resistance is measured in Ohms. Common resistors are characterized by color codes painted on the surface of the resistor. Spectrometer A spectrometer consists of a focusing tube, called a collimator, a telescope, and a vernier scale.
Light passes through the collimator and is focused on a refracting or diffracting material.
This allows one to determine quite accurately the angle of refraction or diffraction of the material in question. Variable Resistor A variable resistor is, as the name suggests, a resistor which allows the user to select the amount of resistance produced in the circuit. This is done by several different methods, depending on the accuracy and quality of the variable resistor. One method is to have a long strand of resistor material, and move one of the contact points, the other being fixed at the far end of the slab, so that the current must pass through more, or less, of the resistive material. Variac Variac is an acronym for VARI able A lternating C urrent.