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# Charges and Their Interactions

The motion of charged matter underlies many things we enjoy like phones and plasma globes. It also puts a permanent end to the enjoyment of some 6,000 people per year, as fatal lightning strikes.

# Electric charge

A nail with a mass of $$17 \text{ g}$$ is charged with $$- 2.24 \times 10^{-13} \text{ C}.$$ How many excess electrons are in the nail?

The elementary charge is $$e=1.60 \times 10^{-19}\text{ C}.$$

How many excess electrons are there on a tiny, spherical water drop of charge of $$-4.00 \times 10^{-16}\text{ C}?$$

The elementary charge is $$e=1.60 \times 10^{-19}\text{ C}.$$

If a current of $$0.30\text{ A}$$ flows for $$2.50\text{ min}$$ in a conducting wire, approximately how many conduction electrons pass through the wire?

The elementary charge is $$e=1.60 \times 10^{-19}\text{ C}.$$

Suppose there is a small (copper) coin with a mass of $$25 \text{ g}.$$ If we want to leave it with a charge of $$+1.4 \times 10^{-7}\text{ C},$$ approximately how many electrons must be removed from that metal coin?

The elementary charge is $$e=1.60 \times 10^{-19}\text{ C}.$$

If an average current of $$0.07\text{ A}$$ flows from a conducting sphere for $$5\text{ sec}$$ and then stops, what can we know about the sphere?

The elementary charge is $$e=1.60 \times 10^{-19}\text{ C}.$$

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