#2 #6 #8 #12 #222. How many electrons does it take to make 1 C?
Recalling that an electron carries the elementary charge e (see the inside cover of the back of your textbook) we write
6. In an ionic solid such as table salt (NaCl) an electron is transferred from one atom to the other. If the atoms are separated by a distance of 0.1 nm, how strong is the electric force between them?
Since a single electron is transferred, we have two charges - one with a charge of +e and the other of charge -e. The attractive force between these two charges is computed below.
8. Calculate the ratio of the electric force to the gravitational force between two electrons.
Consider the ratio of the electric and gravitational forces between two particles separated by a distance r.
Since we have two electrons, this ratio is as shown below.
12. What is the electric field at a distance of 0.2 nm from a carbon nucleus containing 6 protons and 6 neutrons?
Here, we have a single charge of +6e. The electric field points out, away from the nucleus since the charge is positive.
22. How far can a spark jump in dry air if the electric potential difference is 8,000,000 Volts? (This is the reason why high-voltage sources are surrounded by a vacuum or an insulating fluid.)
This problem relates to the last topic in this chapter. In that section we are told (on page 463) that dry air breaks down when the electric field is about 30,000 Volts/cm, so
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