A laboratory experiment on the application of Stefan’s law to tungsten filament electric lamps

Abstract

Commercially available electric lamps are used in a laboratory experiment for the verification of Stefan’s law. Assuming that the emissivity of tungsten filament remains constant and that all the filament power goes out as radiation, Stefan’s T4 law can be verified from a log-log plot of radiated power P against temperature T of the filament. It is found that correction to filament power due to convection loss is necessary for the gas-filled lamps and not for vacuum lamps. The experimental value of the slope of the graph of log P vs log T for all these lamps is found to be 5, which shows that the emissivity of the filament surface is proportional to the temperature of the filament. A simplified laboratory experiment avoiding temperature calculations and convection loss corrections is described in this study.

Deteção da radiação térmica emitida por um filamento de tungstênio aquecido

“…Desde há várias décadas que foi reconhecido que o filamento de tungsténio de uma lâmpada de incandescência poderia ser utilizado como radiador sendo usado em experiências de verificação da lei de StefanBoltzmann [3][4][5][6][7][8]. Uma das principais vantagens da sua utilizaçãoé a possibilidade de controlo e medida da temperatura do filamento a partir das medidas…”

“…em que αé o coeficiente térmico de resistência, e ρ a resistividadeà temperatura T. Para o tungsténiò a temperatura ambiente α = 0, 0053 K −1 [4,8]. Para variações da ordem das dezenas ou centenas de kelvin, esta lei nãoé válida sendo necessário recorrer a tabelas de valores medidos ou a expressões empíricas ajustadas a esses dados [9].…”

Study of Heat Loss from Hot Tungsten Filament Bulb Using AT89C51 Based Data Acquisition System

“…The experiment using a tungsten bulb in a simple ammeter-voltmeter setup which includes an autotransformer for voltage variations [2,3] is advantageous than Wheatstone bridge setup [1].But the experiment using autotransformer is dangerous while compared with the Wheatstone bridge method. The simple circuit with voltmeter and ammeter with dc power supply is preferable for the student experiment [4, 5 and 7].…”

“…The work done by various workers [1][2][3][4][5][6][7] in this direction is given in the form of literature review as given …”

“…[3] In this experiment tungsten bulb is used in a simple ammeter-voltmeter setup which includes an autotransformer. From the hardware the readings of V and I, resistance of the filament and power dissipated are measured.…”