KVPY SX SB Exam 2018 Question Paper

Question : 95 of 120

Marks: +1, -0

Two rods of copper and iron with the same cross sectional area are joined at S and a steady current I flows through the rods as shown in the figure.

Choose the most appropriate representation of charges accumulated near the junction S.

Solution:

Gauss Law

–E_\Cu A + E_\Fe A = q_\en/{∈_0}

\;\;\;J = σE

{-IA}/{σ_\Cu A}+{ IA}/{Aσ_\Fe}=q_\en/{∈_0}

\;\;\;I/A=σE

I\ ∈_0[1/σ_\Fe-1/σ_\Cu]=q_\en

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