Figure shows a thick copper rod X and a thin copper wire Y, joined in series. They carry a current w

Question

Figure shows a thick copper rod X and a thin copper wire Y, joined in series. They carry a current which is sufficient to make Y much hotter than X. Which one of the following is correct?

Accepted Answer

The number density n of conduction electrons in the copper is a characteristic of the copper and is about 10²⁹ at room temperature for both the copper rod X and the thin copper wire Y.
Both X and Y carry the same current I since they are joined in series.
From I = neAv_d
We may conclude that rod X has a lower drift velocity of electrons compared to wire Y since rod X has larger cross-sectional area. This is so because the electrons in X collide more often with one another and with the copper ions when drifting towards the positive end. Thus, the mean time between collisions of the electrons is more in X and than in Y.

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