Voltage
line integral of the electric field strength / From Wikipedia, the free encyclopedia
Voltage is what makes electric charges move. It is the 'push' that causes charges to move in a wire or other electrical conductor. It can be thought of as the force that pushes the charges, but it is not a force. Voltage can cause charges to move, and since moving charges is a current, voltage can cause a current.
Electric Potential Difference is the true scientific term but is commonly called Voltage. Informally, voltage or electric potential difference is sometimes called "Potential Difference". Voltage is also called, in certain circumstances, electromotive force (EMF).
Voltage is an electrical potential difference, the difference in electric potential between two places. The unit for electrical potential difference, or voltage, is the volt. The volt is named in memory of Alessandro Volta. One volt equals one joule per coulomb. The symbol for the unit volt is written with an uppercase V as in (9V). According to the rules of the International System of Units, the symbol for a unit with a name derived from the proper name of a person is uppercase.
Please note that the volt and voltage are two different things. The volt is a unit by which we measure something. Both electric potential and voltage are things we measure and the volt is the unit of measure for both. The symbol for the unit volt is written with a V (9 volts or 9 V). When voltage is used in a formula, it can be typeset in italics, e.g., , or written in cursive. If there is only a single letter symbol to go by, a lowercase v may be used, e.g., or . Electrical engineers use the symbol for voltage, e.g., , to make the difference between voltage and volts very clear.
Technically, the voltage is the difference in electric potential between two points and is always measured between two points. e.g. between the positive and negative ends of a battery, between a wire and the ground, or between a wire or a point of a circuit and a point in another part of the circuit. In everyday use with household electricity in the U.S. the voltage is most often 120V. This voltage is measured from the electric wire to the ground.
Note that there must be both voltage and current to transfer power (energy). For example, a wire can have a high voltage on it, but unless it is connected, nothing will happen. Birds can land on high voltage lines such as 12kV and 16kV without dying, because the current does not flow through the bird.
There are two types of voltage, DC voltage and AC voltage. The DC voltage (direct current voltage) always has the same polarity (positive or negative), such as in a battery. The AC voltage (alternating current voltage) alternates between positive and negative. For example, the voltage from the wall socket changes polarity 60 times per second (in America) or 50 times per second (UK and Europe). The DC is typically used for electronics and the AC for motors.