✔ 最佳答案
(2-3) Lb/La=4, Da/Db=2, Ra=10, Rb=?R=ρL/A=ρL/(πD^2/4)=(4ρ/π)*(L/D^2)=k*L/D^2......k=4ρ/π=常數=> Rb=Ra*(Lb/La)*(Da/Db)^2=10*4*4=160Ω
(2-4) R1=10Ω, D1/D2=3, L2/L1=?, R2=?V=體積固定=A*L=(πD^2/4)*L=(π/4)*(L*D^2)=> L=k1/D^2......k1=4V/π=常數=> L2/L1=(D1/D2)^2=3^2=9R=ρL/A=ρL/(πD^2/4)=(4ρ/π)*(L/D^2)=k2*L/D^2......k2=4ρ/π=常數=> R2=R1*(L2/L1)*(D1/D2)^2=10*9*9=810Ω
(3-1) R1=50Ω, L2/L1=4, D2/D1=?, R2=?V=體積固定=A*L=(πD^2/4)*L=(π/4)*(D^2*L)=> D=k1/L.....k1=√(4V/π)=常數=> D2/D1=√(L1/L2)=√(1/4)=1/2R=ρL/A=ρL/(πD^2/4)=(4ρ/π)*(L/D^2)=k2*L/D^2......k2=4ρ/π=常數=> R2=R1*(L2/L1)*(D1/D2)^2=50*4*4=800Ω
(3-2) L=8m, A=1mm^2=10^(-6)m^2, R=0.5Ωρ=RA/L=0.5*10^(-6)/8=6.25*10^(-8)Ω.m