Basic Definition of Alternating current or what is Alternating Current:

As the name suggests, alternating current or AC means which reverses its direction after a certain interval of time or periodically. Our home appliances run on AC.

Basic Definition of Direct current or what is Direct Current:

As the name suggests, in simple terms, in direct current the current flow in a single direction or is not variable. Battery run on DC.

Advantages of ac over dc:

1. We all know that we got ac supply in our homes and we got this supply by transmitting ac over long distances. AC can be transmitted using step up transformers but direct current or dc can not be transmitted by this method.
2. The ac is easy to generate than dc.
3. It is cheaper to generate ac than dc.
4. The ac generators have higher efficiency than dc.
5. The loss of energy during transmission is negligible for ac.
6. The ac can be easily converted into dc.
7. The variation of ac can easily be done using transformers either step up or step down.
8. The value or magnitude of ac can be decreased easily without loss of excess of energy. This can be done by using choke coil.

These are the 8 advantages of ac over dc. There are disadvantages of ac over dc also. If you know more advantages of AC over DC, please mention it in the comment section.

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On the basis of conductivity ,the materials can be classified in to following categories:-

(a)    Conductors:- These are those materials whose electrical conductivity is very high. Conductors conduct charges very easily . For super-conductor , the value of electrical conductivity is infinite.

Examples. Copper,Silver.Aluminum,Tungsten etc.

(b)   Semiconductors:- They are those materials whose electrical conductivity lies in between insulators and conductors . Semiconductors can conduct charges but not so easily as in case of conductivity.

Examples. Germanium.Silicon etc.

(c)    Insulators:- These are those materials whose electrical conductivity is either very very small or nil. Insulators do not conduct charges.

Examples. Glass,Rubber,Wood etc.

ELECTRIC CURRENT

Definition. Electric current is defined as the rate of flow of electric charge q, that is

I=q/t

The unit of current is ampere ,A

If the current is not varying with time , then the current is called steady electric or stationary current.

In the conductors ,current is due to motion of electrons .In gases , the charge is carried by electrons and positive ions.In Liquids, the charge is carried by positive and negative ions. In semiconductors ,the movement in charge is due to electrons and holes.

Types Of Current.The electric current can be classified into the following categories:-

(i) Steady current:- The current whose magnitude does not change with time is called Steady current. The variations between current(I) and time(t) for a steady current will be a straight line.

(ii) Varying current:– The current whose magnitude changes with time is called varying current. T

(iii) Alternating current:-The current whose magnitude changes continuously with time and direction changes periodically is called alternating current. Such a current is represented by a sine curve or cosine curve .The variation of I with t for sinusoidal alternating current is shown in fig

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