Coulomb's Law (Electric Force) Video Lessons

Concept

Problem: Two small aluminum spheres, each of mass 0.0250 kilograms, are separated by 80.0 centimeters.a. How many electrons does each sphere contain? (The atomic mass of aluminum is 26.982 grams per mole, and its atomic number is 13.)b. How many electrons would have to be removed from one sphere and added to the other to cause an attractive force between the spheres of magnitude 1.00 × 104 N( roughly one ton)? Assume that the spheres may be treated as point charges.c. What fraction of all the electrons in one of the spheres does this represent?

FREE Expert Solution

a.

Number of electrons, Ne:

$\overline{){{\mathbf{N}}}_{{\mathbf{e}}}{\mathbf{=}}{\mathbf{n}}{{\mathbf{N}}}_{{\mathbf{A}}}{\mathbf{Z}}}$

Number of moles, n:

$\begin{array}{rcl}\mathbf{n}& \mathbf{=}& \frac{\mathbf{m}}{\mathbf{M}}\\ & \mathbf{=}& \frac{\mathbf{0}\mathbf{.}\mathbf{0250}}{\mathbf{26}\mathbf{.}\mathbf{982}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{3}}}\end{array}$

n = 0.9265 mol

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Problem Details

Two small aluminum spheres, each of mass 0.0250 kilograms, are separated by 80.0 centimeters.

a. How many electrons does each sphere contain? (The atomic mass of aluminum is 26.982 grams per mole, and its atomic number is 13.)

b. How many electrons would have to be removed from one sphere and added to the other to cause an attractive force between the spheres of magnitude 1.00 × 104 N( roughly one ton)? Assume that the spheres may be treated as point charges.

c. What fraction of all the electrons in one of the spheres does this represent?