====Description====
The [[IV Graph]] for a '''bulb''' shows that:
*As [[Potential Difference|potential difference]] increases, [[Electrical Current|increasescurrent]]increases.
*At small [[Potential Difference|potential differences]]] the the relationship between [[Potential Difference|potential difference]] and [[Electrical Current|current]] is [[linear]] (the [[gradient]] is constant).
*At large [[Potential Difference|potential differences]] the [[gradient]] becomes more shallow as the [[Electrical Resistance|resistance]] of the '''bulb''' increases.
====Explanation====
: * At small [[Potential Difference|potential differences]] there is a small [[Electrical Current|current]] so the [[heating]] effect of the [[Electrical Current|current]] is small and the [[filament]] remains at a low [[temperature]].: * At large [[Potential Difference|potential differences]] there is a large [[Electrical Current|electrical current]] so the [[heating]] effect of the [[Electrical Current|current]] is large which causes the [[filament]] to be a high [[temperature]].:: ** This is caused by [[electron]]s in the [[wire]] [[collide|colliding]] with [[ion]]s in the [[metal]] [[lattice]] causing them to [[vibrate]].: * [[Wire]]s (like the [[filament]]) have a greater [[Electrical Resistance|resistance]] at higher [[temperature]]s, causing the increase in [[Electrical Current|current]] to be reduced.:: ** This is because the more the [[ion]]s in the [[metal]] [[lattice]] [[vibrate]] the more likely [[electron]]s are to [[collide]] with them and slow down. ====Obtaining the IV Graph===={| class="wikitable"|-|[[File:BulbIVGraphCircuit.png|center|300px]]| style="height:20px; width:300px; text-align:left;" |#Connect an [[ammeter]] in [[Series Circuit|series]] with the '''bulb''' to measure [[Electrical Current|current]] through the '''bulb'''.#Connect a [[voltmeter]] in [[Parallel Circuit|parallel]] with the '''bulb''' to measure the [[Potential Difference|potential difference]] across it.#Use a [[Variable Resistor|variable resistor]] in [[Series Circuit|series]] with the '''bulb''' to vary the [[Potential Difference|potential difference]] across the '''bulb'''.#Start with a [[Potential Difference|potential difference]] of zero and increase the [[Potential Difference|potential difference]] by an interval of 1V up to 10V.#Recording the reading on the [[voltmeter]] and [[ammeter]].#Reverse the connections on the [[battery]] and repeat steps 4 and 5 to find the I-V relationship for negative [[Potential Difference|potential difference]] and [[Electrical Current|current]].|} ==Beyond the Curriculum=={{#ev:youtube|https://www.youtube.com/watch?v=oCEKMEeZXug}}