plz help ty contains a uniform density of charge carriers. The wires are all ele

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plz help ty

contains a uniform density of charge carriers. The wires are all electrically neutral: only the mobile charges are shown. Note that Wire D contains both positive and negative mobile charge carriers, Wire A contains a total of 8 charges in its cubical volume (four shown and four more behind them in the page). Wires B C both only contain one charge-carrier in its volume. Wire D contains one positive and one negative charge carrier in its volurne. The length of each side of wire c is half that af Wires A, B, and D The same voltage is applied across each wire, which results in the same drift velocity. (a) Rank the current density in each wire, greatest first. Explain briefly,

Explanation / Answer

a. Current density is defined asCurrent per Unit area of conductor. Let "a" be the side length of the square (cross-section) conductor A, B & D and "a/2" for Conductor C. Therefore cross-sectional Area for A, B & D is a2, whereas for C is a2/4.

Current in A is 8e, B is e, C is e, D is 2e (one negative and one positive) (where e stands for charge carrier)

Current Density for A is 8e/a2, B is e/a2, C is 4e/a2 & D is 2e/a2

In Decreasing Current Density Order A > C > D > B

b. Current wise A > D > B = C

As shown above maximum number of carriers are in wire A (8e), then in D (2e), then equal in B & C (1 negative)

c. Resistivity of wire is inverse on conductivity of wire. Conductivity of the material is its ability of conduct electricity i.e. number of charge carriers. In other words conductivity is directly proportional to Charge Density. Hence Resistivity is inversly proportional to Charge Density

Order of Resistivity will be B > D > C > A.

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