Reference On Electricity, Part 2 | From - Expert Contractors

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Resistance is the friction or opposition to the flow of current by the wires and transformers, analogous to plumbing installation, where the flow of water is subjected to resistance caused by friction between the water and the inside wall of the pipe, and the various form of turns and fittings. For direct current (DC electricity), the term Resistance is used for friction and Impedance for alternating current (AC electricity).

Factors that Influences Conductors Resistance.

1. Compostion of the Conductor. This refers to a conductor having free electrons that has low resistance.

2. Length of Wire. The longer the wire, the higher is the resistance.

3. Cross Section Area of Wire. The bigger the cross sectional area of wire, the lower its resistance.

4. Temperature. Metal offers high reistance to high temperature (heat).

1.3 Electric Current

By definition, Electric Current is the flow or rate of flow of electric force in a conductor. A current will only flow if a curcuit is formed comprising a complete loop and contains all the following required components.

1. Source of Voltage
2. A closed loop of wiring
3. An electric load
4. A means of opening and closing the circuit

Electric Current is Classified as:

1. Direct Current (DC)
2. Alternating Current (AC)

Direct Current. The DC electricity, flows in one course. Arise is said to be from denial to sure. The usual find of dC electricity, is the dry booth or storage thrash.

Alternating Current: The AC electricity constantly reverses its trend or emanate. Device generated it called generator. This kind of present is universally accepted because of its unlimited number of applications which the following advantages.

1. It is simply produced.
2. It is cheaper to avow.
3. It could be transformed into superior voltage.
4. It could be distribution to far aloofness with low voltage globule.
5. It is more efficient compared with the done flow.

Once a big controversy ensued between the proponents of the DC electricity led by Thomas Edison and the advocates of the AC electricity led by George Westinghouse. According to Thomas Edison, "The AC electricity is risky, because, if involves high voltage transmission line."



The AC advocates on the other hand, countered that:

"The AC alternation if just like a handsaw which cuts on the upstroke and the down stroke. The high voltage in the transmission line could be reduced to the desired voltage as it passes the distribuiton line."

Alternating Current or Voltage is a current or voltage that changes in strength according to a sine curve. An alternating current AC reverses its polarity on each alternation and reverses its direction of flow for each alternation. The AC current goes through one positive loop and one negative loop to form one complete cycle that is continuously repeated.

The number of times this cycle of plus and minus loop occur per second is called the Frequency of alternating current AC expressed in cycles pre second normally referred to as Hertz (hz) named after H. R. Hertz. The frequency of the Direct Current DC is obviously zero Hertz. The voltage is constant and never changes in polarity.