I-V graph explained ✅

Added: 2026-06-03

[00:00:00]The required practicals that comes up in the electricity topic is all about current and voltage or potential difference graphs for different components. This question asks us to sketch out a graph for what it looks like for a filament lamp. Now, in a filament lamp, it is a non-ohmic component. Ohmic components follow Ohm's law, and that means that these two things, voltage and current, are directly proportional across them. In this case, that's not the case because it's non-ohmic. So, the shape looks a bit like this. You do it with a pencil, obviously. Take your time to make sure you're getting your two marks for this question. I've already messed up a bit there. Should have gone through the middle.

[00:00:34]Uh and it goes curves off at this end here.

[00:00:36]Let me explain why this happens. So, there's a bit of a the graph where it follows Ohm's law. However, once potential difference increases past a certain point, the current you'll see stops increasing. That happens because in a bulb, which is these old-school type bulbs here, when you run current through them and potential difference, they obviously glow, but they glow and get hot at the same time. This filament gets really hot. So, as the electrons pass through, as the potential difference is increasing, if things get hot, it means that the particles inside them are vibrating. The metal ions inside the filament are vibrating more and more as the temperature is going up.

[00:01:11]So, as the temperature goes up, the electrons are going through, they are finding it harder to get through. So, temperature goes up, there's basically more resistance. So, that means that the current stops increasing. It doesn't go down, but just stops increasing with potential difference.

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