Question

Answer 1

\(S=\pi\dfrac{d^2}{4}=\pi\dfrac{2^2}{4}=3,14\left(mm^2\right)\)

\(R=\rho\dfrac{l}{S}=2,8.10^{-8}.\dfrac{6,28}{3,14.10^{-6}}=0,056\left(\Omega\right)\)

Answer 2

Bài 5:

a. \(I=I1=I2=0,6A\left(R1ntR2\right)\)

\(R=U:I=12:0,6=20\Omega\)

\(\Rightarrow R2=R-R1=20-7,5=12,5\Omega\)

b. \(R=p\dfrac{l}{S}\Rightarrow S=\dfrac{p.l}{R}=\dfrac{4.10^{-7}.75}{30}=1.10^{-6}\left(m^2\right)=1\left(mm^2\right)\)