Light bulb exponent-rules for the classroom

Exponent-rules are known to describe experimentally how the observables related to incandescent lamps alter with the change in the rated voltage. Pedagogical derivation of the rules for typical observables like the life, lumens, power, etc. in the case of vacuum bulbs is presented. This is achieved by assuming a steady-state operation of the bulb, parameterizing intrinsic properties of tungsten as suitable powers of temperature, and eliminating the temperature between those observables for which the exponent-rules are sought.