You have learned that three important measurements in electricity are as follows:
The volt is the practical unit of measurement of pressure;
The ampère is the practical unit of measurement of the rate of flow; and
The ohm is the practical unit of measurement of resistance.
III
MAGNETISM
Now we will try to explain to you something about magnets and magnetism. There are very few boys who have not seen and played with the ordinary magnets, shaped like a horseshoe, which are sold in all toy-stores as well as by those who sell electrical goods.