1 %AV |11.V;IVthen total charge which crosses the section in time dt is dq = nAevdt. Since current is the rate of flow of charge,it is given asdg nAevdt= nAevdtdtCurrent density, J == nev ampere/metreAssuming a normal current density J= 1.55 x 10° A/m?, n = 10° for a copper conductor and e =1.6 x 10-19coulomb, we get1.55 x 10 = 1029 x 1.6 x 10-19 × vv = 9.7 x 10-5 m/sExample 3:The charge flowing through the imaginary surface in Fig. 7 is 0.16 C every 64 ms. Detemine the current inamperes.Example 4:Determine the time required for 4 x 101 electrons to pass through the imaginary surface in Fig. 7 if the currentis 5 mAExample 5:A conductor material has a free-electron density of 1024 electrons per metre', when a voltage is applied, a constantdrift velocity of 1.5x10° meter/second is attained by the electrons. If the cross-sectional area of the material is 1cm?, calculate the magnitude of the current. (Answer: I=0.24 A)Example 6:A copper wire of are 5mm2 has a current of SmA following through it. Calculate the current density?4. Resistance:The flow of charge through any material encounters an opposing force similar in many respects to mechanicalfriction This opposition, due to the collisions between electrons and between electrons and other atoms in thematerial, which converts electrical energy into another form of energy such as heat, is called the resistance ofthe material. The unit of measurement of resistance is the ohm, for which the symbol isletter omegathe capital GreekThe resistance of any material with a uniform cross-sectional area is determined by the following four factors(see Fig. 8):1. Material2. Length3. Cross-sectional area4. TemperatureAt a fixed temperature of 20°C (room temperature), the resistance is related to the other three factors by6/14056414II

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Answered: Example 3: The charge flowing through…

Example 3: The charge flowing through the imaginary surface in Fig. 7 is 0.16 C every 64 ms. Determine the curent in amperes.

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter28: Current And Resistance

Section: Chapter Questions

Problem 65PQ

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