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Question 26.1: During the 4.0 min a 5.0 A current is set up in a wire, how ......

During the 4.0 min a 5.0 A current is set up in a wire, how many (a) coulombs and (b) electrons pass through any cross section across the wire’s width?

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(a) The charge that passes through any cross section is the product of the current and time. Since t = 4.0 min = (4.0 min)(60 s/min) = 240 s,

q = it = (5.0 A)(240 s) = 1.2 × 10³ C.

(b) The number of electrons N is given by q = Ne, where e is the magnitude of the charge on an electron. Thus,

N=q / e=(1200 \,C ) /\left(1.60 \times 10^{-19} \,C \right)=7.5 \times 10^{21} .

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