Fundamentals 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 Influence Conductors Resistance:

Composition of the Conductor. This refers to a conductor having unbound electrons that has low resistance.
Length of Wire. The longer the lead, the upper is the resistance.
Cross Section Area of Wire. The superior obstruct sectional matter of wire, the lesser its resistance.
Temperature. Metal offers high resistance to high temperature (warm).
1.3 Electric Current

By definition, Electric Current is the gush or toll of drift of thrilling cogency in a conductor. A modern will only flood if a circuit is created composing a broad ball and contains all the next necessary components.

1. Source of Voltage
2. A bunged circle of wiring
3. A thrilling freight
4. A means of aperture and last the trail

Electric Current is Classified as:

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

Direct Current. The DC electricity, flows in one direction. The flow is said to be from negative to positive. The normal source of a DC electricity, is the dry cell or storage batter.

Alternating Current. The AC electricty constantly reverses its direction or flow. It is generated by machine called generator. This type of current is universally accepted because of its unlimited number of applications which the following advantages.

1. It is easily produced.
2. It is cheaper to maintain.
3. It could be transformed into higher voltage.
4. It could be distribution to far distance with low voltage drop.
5. It is more efficient compared with the direct current.

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 dangerous, 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.