1. Filament There is a significant surge when a filament lamp is first switched on. Propose a theoretical model and investigate it experimentally. Swiss.

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Presentation transcript:

1. Filament There is a significant surge when a filament lamp is first switched on. Propose a theoretical model and investigate it experimentally. Swiss Team, Seoul 2007

Theory cold hot The resistivity depends on the temperature! Swiss Team, Seoul 2007

Theory How does the resistance depend on temperature? Approximation (based on measured data): Swiss Team, Seoul 2007

Theory γ · R0 β· R0 α · R0 Resistance Swiss Team, Seoul 2007 Midwest Tungsten Service, Willowbrook, USA; www.tungsten.com

Energy PR PE PH Swiss Team, Seoul 2007

Theory PE = electric power PR = radiation power PH = heat power V = Voltage R = Resistance ε = emissivity of Tungsten σ = Stefan – Boltzmann constance = 0.567·10-7 W·m-2·k-4 A = surface c = heat capacity = 134 J·kg-1·K-1 m = mass Swiss Team, Seoul 2007

Theory How does the temperature change? T0=293.15K  ΔT=37.7K (timestep 1 ms) T1=T0 + ΔT …. Swiss Team, Seoul 2007

Filament Length of the filament: Number of turns n = 140 Surface: 0.15mm d=0.03mm Length of the filament: Number of turns n = 140 Surface: Volume: Mass: d length 0.15mm Swiss Team, Seoul 2007

Emissivity of Tungsten Definition: The emissivity is a dimensionless coefficient which describes the radiation of an object. It depends on the surface, the temperature and the material.

Measuring emissivity Stationary current: constant temperature Therefore we can calculate the emissivity for different temperatures from our measured data.

Emissivity Accepted value: ε = 0.33 at 2700 K  reasonable results Swiss Team, Seoul 2007

Calculations Numerical calculation of T(t) using Maple I(t) = V/R(T(t))

Calculation: Temperature Swiss Team, Seoul 2007

Calculation: Current Swiss Team, Seoul 2007

Experiments Experiment 1: Stationary current (test of reliabilty of the numerical calculation) Experiment 2: Current surge after switching on

Experiment 1: Current vs. Potential Voltage source Voltmeter Ammeter Swiss Team, Seoul 2007

Experiment: Current vs. Voltage Swiss Team, Seoul 2007

Experiment 2 Voltage source LabPro Switch Voltage probe Current probe Swiss Team, Seoul 2007

Experiment I V LabPro Swiss Team, Seoul 2007

Experiment: Voltage vs. Time Swiss Team, Seoul 2007

Experiment: Current vs. Time Voltage=3V Swiss Team, Seoul 2007

Comparison: Theory – Experiment Swiss Team, Seoul 2007

Summary We established a theoretical model describing the phenomenon. We numerically calculated the temperature and current after switching on the light bulb. Experimental data corresponds very well to our theory and model. Swiss Team, Seoul 2007