2016 2017 ASVAB For Dummies with Online Practice by Rod Powers & Angie Papple Johnston

Author:Rod Powers & Angie Papple Johnston
Language: eng
Format: epub
ISBN: 9781119239260
Publisher: Wiley
Published: 2016-06-20T00:00:00+00:00

Examining the current of the electrical river

Electrons are negatively charged, and they attempt to shift from one atom to the next to the next, trying to get to a positive charge, such as the positive side of a battery. They’re able to shift if the material is a conductor. But if the material is an insulator, the electrons will be much, much less able to shift because of the insulating material’s molecular structure.

Electrical current is the flow — or, more precisely, the rate of flow — of electrons in a conductor. Current flow can be expressed in terms of coulombs (abbreviated C), which measure charge. A coulomb is the amount of electricity provided by a current of 1 ampere flowing for 1 second. It’s called a coulomb because a guy named Charles de Coulomb discovered it in the late nineteenth century, and the rules say that if you discover something, someone will stick your name on it.

If 1 coulomb (about 6,241,500,000,000,000,000 electrons) flows past a specified point in 1 second, that’s a flow rate of 1 ampere (amp, abbreviated A). An ampere represents the strength of a current. For the sake of convenience, electrical currents are measured in amps. Typically current is tiny, so small that it’s measured in milliamperes; 1 milliampere is one-thousandth of an ampere. Current meters, called ammeters, measure the flow of current through a circuit.

The amount of voltage (the difference in potential) and the resistance in a circuit determine the number of amperes along a wire — or whatever you’re using to conduct the electricity from one place to another. More voltage (for instance, a higher-voltage battery) means that more amps flow in a wire (or conductor). You can read more about this relationship in the next section, which discusses Ohm’s law.

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