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Question
Consider two conducting wires A and B of the same diameter but made of different materials joined in series across a battery. The number density of electrons in A is 1.5 times that in B. Find the ratio of the drift velocity of electrons in wire A to that in wire B.
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Solution
In a series circuit current flowing through the entire circuit is exactly the same, hence
`I = n_A A_e(v_d)_A`
= `n_B A_e(v_d)_B`
`((v_d)_A)/((v_d)_B) = n_B/n_A = n_B/(1.5n_B) = 1/1.5`
= `10/15 = 2/3`
`(v_d)_A : (v_d)_B = 2 : 3`
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