Errors in an experiment of ohm's law?

The aim of experiment is To investigate the relationship between voltage and current for both a light bulb filament and an exposed filament. I have to find possible errors. I already found some: 1. The procedure involves using a light bulb, which when an electric current passes through it begins to heat up. Since,... show more The aim of experiment is To investigate the relationship between voltage and current for both a light bulb filament and an exposed filament.
I have to find possible errors. I already found some:
1. The procedure involves using a light bulb, which when an electric current passes through it begins to heat up. Since, temperature is a factor affecting resistance, a drawback of the procedure is that we get an error due to this increase in temperature of the light bulb filament which is not quantifiable.
2. In the case of the bulb filament, this error is not significant in affecting the readings as water has a very high specific heat capacity and absorbs any heat evolved. This cannot be done for the bulb as due to the glass covering and it being filled with an inert gas, the filament still heats up.
3. The formula for calculation of resistance imply standard temperature and pressure i.e. 273K and 1 atmosphere of pressure. However, my experiment was carried out in a temperature in excess of 403K accounting for a deviation from the actual value.
4. The Internal resistance of the battery source was not provided and hence it is an error that is not quantifiable.

Can anyone suggest any other possibel error?
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