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Question 21.59: What is the total charge in coulombs of 75.0 kg of electrons......

What is the total charge in coulombs of 75.0 kg of electrons?

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The mass of an electron is m=9.11 \times 10^{-31} \,kg , so the number of electrons in a collection with total mass M = 75.0 kg is

n=\frac{M}{m}=\frac{75.0 \,kg }{9.11 \times 10^{-31} \,kg }=8.23 \times 10^{31} \text { electrons. }

The total charge of the collection is

q=-n e=-\left(8.23 \times 10^{31}\right)\left(1.60 \times 10^{-19} \,C \right)=-1.32 \times 10^{13}\, C .

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