1. 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

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

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

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

5. Energy PR PE PH
Swiss Team, Seoul 2007

6. 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

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

8. 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

9. 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.

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

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

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

13. Calculation: Temperature
Swiss Team, Seoul 2007

14. Calculation: Current
Swiss Team, Seoul 2007

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

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

17. Experiment: Current vs. Voltage
Swiss Team, Seoul 2007

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

19. Experiment I V
LabPro
Swiss Team, Seoul 2007

20. Experiment: Voltage vs. Time
Swiss Team, Seoul 2007

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

22. Comparison: Theory – Experiment
Swiss Team, Seoul 2007

23. 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