I'm doing a report on my experiment right now where you had to test out the voltage and current of 2 resisters and a light globe with an ammeter and voltmeter. We had to graph the results, and the reisistors had a linear relationship between voltage and current, but the light globe is either exponential or power. Can anyone explain why this is? Is it a systematic error?
Believe your data. The tungsten filament of a light bulb has a resistance that increases with temperature, and as you raise the voltage, the filament becomes much hotter.
Many materials have a resistance that varies with temperture, but the effect is more noticeable with light bulb filaments because they are designed to get very hot, in order to emit light.
So basically, the light bulb's resistance varies?
The differing relationship between voltage and current for the resistors and the light globe is not due to a systematic error. It can be explained by the intrinsic properties of these components.
In a resistor, the relationship between voltage (V) and current (I) is linear. This is because resistors are designed to have a constant resistance, which means the current passing through the resistor is directly proportional to the voltage applied across it, according to Ohm's Law (I = V/R). The resistance (R) remains consistent, resulting in a straight-line relationship between V and I on a graph.
On the other hand, a light globe (incandescent bulb, for example) exhibits a non-linear relationship between voltage and current. This behavior is due to the way a light globe operates. When a voltage is applied to the bulb, the filament inside heats up and emits light. The bulb's resistance changes with temperature, resulting in a non-linear relationship between V and I.
The relationship can be approximated as exponential or power law depending on the specific properties of the light globe. The change in resistance with temperature leads to a non-linear increase in current with increasing voltage. This phenomenon is often represented using exponential or power equations.
To summarize, the linear relationship between voltage and current in resistors is because they have a constant resistance, while the non-linear relationship in light globes is due to the varying resistance caused by temperature changes. This is a fundamental property of these components and not an error in your experiment.