Question

Question 1: a) What are current density and drift speed? Why is the drift speed always smaller than the actual speed of electron? (4) I b) 10.0 m length of wire consists of 4.0 m of copper followed by 6.0 m of aluminum, both of diameter 1.4 mm. A voltage difference of 80 mV is placed across the composite wire (a) What is the total resistance (sum) of the two wires? (b) What is the current through the wire? (c) What are the voltages across the aluminum part and across the copper part? (4)

Answer 1

current density & The amount of charge per unit time that flow through a unit area of a Cross section . It's denoted by (J). J= I 42 is Drift velvaty – Drift velocity average velocity attained by charge particles such as electrons in a material due to electric field. I=0 ne ad t = ne Ave alue Ld Z of election its I= ne Ave Vd The drift velocity is smaller than the actual velocity because th during collisiory electron 1ooo kinetic Energy. As a result election do accelerated but travel with finite average velocity . diameter 1.4mm V= 80 mv Cu R = se Al A

RAL Roo = Scu lu SAI PAL AA Acu Su = DO SAI= 2.65*108 1.68x10-8 ohmm Reu = 1.68X108 X4 * ( 7x10 3/2 Reu= 2.13 x 108 4gx106 Rov z> 4.3x10 RAI = 2.68x108 x 6 * (7x10312 s.ll x108 49x106 10.4x102 Rtotal = Rout RAI 14.7 x 107 Current - 80x10 3 14. 7X107 54.42 A R voltage drip acoso Aluminium RAI XI 56.59 810-4 5x H59 x103 across cupper 56.59 Xlo A Roux I 4.38104 x 54.42 234.006x104 23.4 X103

R = si A R₂ = 8 (24) 4 SL = 4R +4) A R2 = 4R (R increase & times V x I Vxv R - Energy = 12 R resistance change from R to AR then Energy will also decrease also decrease & times. when p=2.0kw l= 80cm V= 120v when 12 Cm remove l2=80-12 = 68cm P= v2 y-A R y2 si A Ri= 12 8 l R2 V2 A 8 l2 2.0 kw = 80 P2 68 Iz ele sta P2 1.7 kw