Thursday, June 23, 2011
5:32 PM | Posted by
Editor in chief |
Before we start we have to know some basic Concepts and common Expression.in this lesson we will speak about voltage and current.
Voltage
Voltage is the potential energy source in an electrical circuit that makes things happen. It is sometimes called Electromotive Force or EMF. The basic unit (measurement) of
electromotive force (EMF) is the volt. The volt was named in honor of Allessandro Volta (1745–1827), the Italian
physicist who also invented the battery. Electrical voltage is identified by the symbol “e” or “E.” (Some references use symbols “v” or “V”.
Voltage is the potential energy source in an electrical circuit that makes things happen. It is sometimes called Electromotive Force or EMF. The basic unit (measurement) of
electromotive force (EMF) is the volt. The volt was named in honor of Allessandro Volta (1745–1827), the Italian
physicist who also invented the battery. Electrical voltage is identified by the symbol “e” or “E.” (Some references use symbols “v” or “V”.
Voltage is the electric power system’s potential energy source. Voltage does nothing by itself but has the potential to do work. Voltage is a push or a force. It always appears between two points.
Normally, voltage is either direct (DC) or alternating (AC).
Electric power systems are based on alternating voltage applications from low-voltage 120 volt residential systems to ultra high voltage 765,000 volt transmission systems. There are lower and higher voltage applications involved in electric power systems, but this is the range commonly used to cover generation through distribution and consumption.
Current
Current is the flow of electrons in a conductor (wire). Electrons are pushed and pulled by voltage through an electrical circuit or closed-loop path. The electrons flowing in a conductor always return to their voltage source. Current
is measured in amperes (amps).The number of electrons
never decreases in a loop or circuit. The flow of electrons in a conductor produces heat due to the conductor’s resistance.
Voltage always tries to push or pull current. Therefore, when a complete circuit or closed-loop path is provided, voltage will cause current to flow. The resistance in the circuit will reduce the amount of current flow and will cause
heat to be provided. The potential energy of the voltage source is thereby converted into kinetic energy as the electrons flow. The kinetic energy is then utilized by the load (consumption device) and converted into useful work.
Current flow in a conductor is similar to ping-pong balls lined up in a tube. Referring to the figure, pressure on one end of the tube (voltage) pushes the balls through the tube. The pressure source (battery) collects the balls exiting the tube and returns them to the tube in a circulating manner
(closed-loop path). The number of balls traveling through the tube per second is analogous to current. This movement of electrons in a specified direction is called current. Electrical current is identified by the symbol “i” or “I.”
Current Flow Versus Electron Flow
Electron flow occurs when the electron leaves the atom and moves toward the positive side of the voltage source, leaving a hole behind. The holes left behind can be thought of as a current moving toward the negative side of the voltage source. Therefore, as electrons flow in a circuit in one direction,holes are created in the same circuit that flow in the opposite direction.
The standard convention used for determining current direction in electric circuits is hole flow!The early experiments
simply defined current flow as being from positive to negative.
Water flow versus Current flow
if you consider the Electric circuit like the water Pump system then the voltage corresponds to the pressure that pushes water through a pipe. The pressure is present even though no water is flowing.the Current corresponds to the water flow. this water flow can't occured without the pressure. the final amount of water depend on both.that's final amount corresponds to Power (we will discuss it in next lesson). Do you feel confused confused about this lesson? Leave your question now in a comment.
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