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Science project idea on how electricity is measured
Measure Electricity Science Project Idea
How electricity is measured: volts, amperes, kilowatts. In all the cells discussed, you have noticed that there has been greater chemical action at the zinc electrode than at the other. This gives rise to what may be called an electrical pressure or electromotive force (E.M.F.) and causes a current somewhat as differences in water pressure will produce a current. This current passes from the zinc to the other electrode within the cell, and from the carbon to the zinc electrode through the wire circuit. The unit of electromotive force is called the volt. It is approximately the electromotive force of the simple voltaic cell. By connecting the several cells in series, that is, by connecting the carbon of one cell with the zinc electrode of the next one, etc., the voltage or electromotive force of the battery of cells will be equal to the sum of the electromotive forces of the individual cells. The electrical pressure is measured by an instrument called the voltmeter. The pressure in a water pipe may be very great, but yet there may be very little, if any, flow of water because the faucet opening is quite small. On the other hand, the pressure may be relatively low with a large flow, providing there is nothing to obstruct the current. In the same way, the amount of electricity that passes through a wire depends upon the voltage or pressure, and upon the resistance. The unit of resistance is called an ohm, in honor of Georg Ohm, an investigator in electricity, who worked during the early part of the nineteenth century.
The unit of current is called an ampere, in honor of another great scientist who was contemporary with Volta and Ohm. The relation of current, electromotive force, and resistance to flow is expressed in Ohm's law:
Current = electromotive force or Amperes = Volts or Ohms = Volts
Resistance Ohms Amperes The instrument used to measure the current is called an ammeter. A rheostat is a device by which the amount of resistance may be controlled. Just as the amount of work done by water power depends upon the pressure and the amount of water, so the work done by an electric current may be determined by multiplying the voltage (pressure) by the amperage (amount of electricity). The unit of work, called a watt in honor of James Watt, is the work done by one ampere having the voltage of 1. Since this is such a small unit, the kilowatt, which is equal to 1000 watts, is more often used. Electrical energy is charged for by the kilowatt hour, which is the energy furnished by a current providing in one hour one kilowatt of work. A kilowatt hour is equal to about 1.333 horsepower (hours), and in New York City costs from 4.5 to 7 cents.
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