Part A A person shuffles across the rug and then place his finger near his frien

Question

Part A

A person shuffles across the rug and then place his finger near his friend's nose, causing a small spark that transfers about 10^9C of charge from the person to his friend. Determine the number of electrons transferred. e=1.6×10^19C.

Express your answer using two significant figures.

Part B

Estimate the fraction of electrons in person's 70-kg body that were transferred to his friend. Note that the electron mass is about 1/20000 the mass of the atom the nuclei are much more massive and the mass of an average atom in the body is about 2×10^26 kg . Assume that each atom has 5 electrons on average. (Note: Don't get hung up on minutia this is a rough estimate.)

Express your answer using one significant figure.

Explanation / Answer

part A)

Q = charge = 10-9 C

e = charge on an electron = 1.6 x 10-19 C

n = number of electrons

Using the formula

Q = ne

10-9 = n (1.6 x 10-19 )

n = 6.25 x 109

Part B)

mass of one atom = 2 x 10-26 kg

mass of body = 70 kg

Total number of atoms in the body = mass of body / mass of one atom = 70 / 2 x 10-26 = 35 x 1026

number of electrons per atom = 5

So total number of electrons = 35 x 1026 x 5 = 175 x 1026

fraction = 6.25 x 109 / 175 x 1026 = 35.71 x 10-20

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