Why do the ammeter readings fot the lightbulb need a short time to stabilize, whereas for a resistor they dont

Question

in a physics experiment i measured voltage using a digital voltmeter and current using an ammeter for a light bulb, which has a non-ohmic behavior. Why does the needle of the ammeter overshoot for about a second before stabilizing?

Answer 1

Well, the filament has a lesser resistance when cold and so the first current when you switch the bulb on is higher and within a fraction of a second stabilises at a lower value once the filament heats up. The needle goes to the higher value and then comes to the lower value.

Also even with a resistor, the ammeter with a mechanical needle will have a slight overshoot because the needle will have some inertia. If the needle is damped, you may find that the needle moves smoothly without oscillating much about its rest value.

Answer 2

It has to do with the tungsten filament. Tungsten like a lot of metals have less resistance when cold and more when they are hot. Also the filament evaporates to some degree with use. It does not do this evenly thus leaving thinner spots on the filament in some areas than others. When the thin spots have reached the temperature that they would be running at, the thicker, heavier parts of the filament have not yet reached their final temperature. This means that the filament's resistance is still a bit low and excessive current is still flowing.
A resistor is made differently and able to handle initial surges of current. Hope this helps.

Answer 3

this is probably coz the buld hs got a different resistance when hot and when cold and thus it changes as the fillament heats up wheas the resistor's is constant. :)