Exercise 25.12 Part A Find the magnitude of the current density in the wire A co

Question

Exercise 25.12 Part A Find the magnitude of the current density in the wire A copper wire has a square cross section 2.2 mm on a side. The wire is 3.6 m long and carries a current of 4.0 A. The density of free electrons is 8.5 × 1020 m Express your answer using two significant figures. J- 17.438-105 A/m Submit My Answers Give Up Incorrect; Try Again; 2 attempts remaining Part B Find the magnitude of the electric field in the wire Express your answer using two significant figures. Submit My Answers Give Up Part C How much time is required for an electron to travel the length of the wire? Express your answer using two significant figures.

Explanation / Answer

area= (2.2 x 10^-3)^2= 4.84 x 10^-6

J = !/A= 4/ (2.2 x 10^-3)^2= 0.826x 10^6 A/ m^2 or 8.26 x 10^ 5 A/ m^2

b)E = J ( resistivty of copper) = (8.26 x 10^ 5 A/ m^2) (1.72 x 10-8) =14,215 x 10^ -3 V/M

c)tim e= length of wire/ drift velocity

drift velocity = I/ (neA) = (4)/(8.5 x 10^ 28 x 1.6 x 10^-19 x4.84 x 10^-6) = 4/ (65.824 x 10^3) = 6.07x 10^-5 m/s

t= 3.6/ ( 6.07x 10^-5 m/s)= 5.93 x 10^ 4 seconds

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