Filament lamp I/V characteristics lab problem.

[karydopita]

i have to have my lab report ready in the next 1 hour and i am stuck. in my experiment we had a varied power supply , an ammeter and a voltmetter both with small error (and digital). i have taken about 15 measurements of potential difference and its respective current. the circuit had in one case a resitor and in the other case a filament lamp. the resistor is an easy one as ohm's law is applied so i sketch the graph with my logger pro and take the 1/slope(gradient) to find R. my problem however is when it comes to the filament lamp. i am not sure if i should use a square or a linear or some other fit. also i don't know whatresult from the graph should i use to find resistance if the graph isn't linear. also in a filament lamp which is a non ohmic device can i use R=V/I? please help me out with this one.
in general: can someone help me with finding the resistance of a filament lamp based on the measurements i have take?
and also can someone tell me what the error is when i have +/- 0.01 Volts for potential differnce and +/- 0.1 mA (NOT Amber)?
thank you very much...

 

[jbsteele]

When dealing with a filament lamp, it is important to note that it is a non-ohmic device, meaning that Ohm's law cannot be applied to calculate its resistance. In order to determine the resistance of the filament lamp, you need to use a graphical method. Using your data points, you can plot the potential difference (V) versus the current (I), and then use a least-squares regression to determine the best fit for the data. Depending on the data points, you may need to use a linear fit, but you may also need to use a higher order polynomial fit. Once you have determined the best fit for the data, you can use the formula for the line of best fit to calculate the resistance of the filament lamp.As for the errors in your measurements, since you are measuring the potential difference (V) with an accuracy of +/- 0.01 Volts and the current (I) with an accuracy of +/- 0.1 mA, you can expect the overall error in the resistance measurement to be around 0.1 mOhms.