Answer:
Option C, the current is constant through the wire.
Explanation:
Ok, so we know that as larger cross-section we have, smaller resistance, so makes sense to think that the current will be larger in the first piece of wire.
But now let's think in a simpler case.
Suppose that in the image we see pipes, and through these pipes, there is water flowing.
You would say that the water flow in WX is larger than the current in XY?
No, it can´t be, the volume of water that leaves WX in a lapse of time Δt, must be the exact same volume of water that enters XY in that lapse of time, then the water flow is constant.
The only thing that can happen is that the velocity at which the water moves in WX is smaller than the velocity at which the water moves in the other parts.
The same thing happens here, the current will be constant, and the thing that changes is the velocity at which the electrons flow in each part of the wire.
So if you actually had a wire like this, you would see that the thinner parts heat a lot more than the others, and this happens because the electrons in those parts have a lot more kinetic energy.
The correct graph is C.
