Norman Thiberge, age 15, of Belmont, Fl. for his question:
What are ohms?
Our knowledge of electricity has grown bit by bit through the centuries. As information accumulated, it became necessary to find units of measurement for electrical force. We do honor to some of the early contributors to our knowledge of electricity by using their names for these units of measurement.
The volt was named for Alessandra Volta, the ampere for Andre Ampere. The ohm, a unit of electrical resistance, was named for the German scientist Ohm, who showed that even a copper wire shows some resistance to the electric current it carries,
In some respect, an electric current may be compared to a water main. The main may be carrying water along at the rate of a hundred barrels a minute. The wire may be carrying one hundred amperes' which is an electric current at the rate of one hundred units of electricity a second.
Both the water and the electricity need a push before they will flow along. The water gets this push from pressure. The electricity gets its push from a battery or ,generator, The amount of power or push given to the electric current is calculated in terms of volts.
We have known for almost 150 years that an electric current is very.choosy about the substances through which it will and will not flow. It refuses to pass through glass, porcelain and rubber. These substances are called insulators, or poor conductors of electricity„ It passes freely, or almost freely, through copper, silver and aluminum. These are called the good conductors of electricity.
In the I820’s, a German scientist named Ohm showed that a current of electricity was hampered to some degree even in such a good con¬ductor as copper. Some of the voltage, or push, behind the current seemed to be getting lost on the way between the generator and the light bulb. Ohm showed that an electric current meets with some resistance from the copper itself. A longer wire has more resistance than a shorter one a thin wire has more resistance than a thick wire.
This resistance is calculated in units for purposes of measuring. The unit is named in honor of the discoverer of the resistance force. In calculating the number of usable amperes in a current, both the voltage and the resistance must be taken into account. The number of volts is divided by the number of ohms and the answer given in amperes.
Suppose your electric toaster has a resistance of 20 ohms and you plug it into a line carrying 130 volts. The usable amount of electricity in the toaster would be 5.5 amperes.