Voltage, current, and resistance are the three basic
building blocks required to manipulate and utilize electricity.
Voltage, also known as electric potential difference,
electric pressure, or electric tension, is denoted by ∆V. It is the difference
in electric potential energy between two points per unit electric charge. Usually,
voltage is caused by a combination of static electric fields, electric current
through a magnetic field, and time-varying magnetic fields. We use voltmeters
to measure the voltage between two points in a system. Often, we use a common
reference potential – such as the ground of the system – as one of the points.
A voltage may represent or lost, used, or stored energy.
An electric current is a flow of electric charge carried by
electrons moving along a wire. The unit for measuring an electric current is
the “ampere,” which is the flow of electric charge across a surface at the rate
of one coulomb per second. Electric current is measured using an ammeter.
Electric currents allow incandescent light bulbs, motors, inductors and
generators to exist and function as they do.
The resistance of an object is the measure of how difficult
it is to pass an electric current through that object. The unit by which
electrical resistance is measured is “ohm” (Ω). An object of uniform cross
section has a resistance proportional to its resistivity and length and
inversely proportional to its cross-sectional area. All materials show some level
of resistance.
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