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INSTANTSUPPORT Mastering Physics: Ch 18 HW - Internet Explorer provided by TOSHIBA is https/session mastering physics.com/myct/itemView?assignmentProblemID=85614116&offsets; next Ch 18 HW Problem 18.55 W Problem 18.55 Part A Estimate the electron drift velocity. Assume one free electron per atom. A 0.69-mmdiameter copper wire carries a tiny current of 2.5 puA. The molar mass of copper is 63.5 g/mole and its density is 8900 kg/m. NA = 6.02 x 1024 . Express your answer to two significant figures and include the appropriate units. THWA s n o e ? r ar, BP x to a 2 4 - 9m 5.25. 10 Submit by Answers Give Ue. IncorrectTry Again; 2 attempts remaining 22.11 H 2 to 10/12/2017

Explanation / Answer

Given Data

Diameter of the copper wire = 0.69mm

so , area =pi/4d^2

             = pi/4 * (0.69*10^-3)^2

             = 3.74*10^-7 m^2

current = 2.5 uA = 2.5*10^-6 A

molar mass of copper M = 63.5g/mole = 0.0635 kg/mole

density = 8900 Kg/m3 , Na = 6.02*10^23

number of electrons drifting = Na*density / M

                                       = (6.02*10^23)*(8900) / (0.0635)

                                     n = 8.44*10^28

Current density =neVd

where Vd = drift velocity

J = I/A = neVd

Vd = I/Ane

Vd = (2.5*10^-6) / [ (3.74*10^-7)*(8.44*10^28) * (1.6*10^-19) ]

Vd = 4.95*10^-10 m/s

the drift velcoity is 4.95*10^-10 m/s

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