Electric current has become our daily life necessity. There are thousands of things around us which are useless without electric current e.g. Computer, tube-lights, bulbs, TV etc. Many appliances use Direct Current and others uses Alternating Current. Now Let me explaing what is Alternating Current and Direct Current.

There are type of Electric Current:

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

Alternating Current(AC):
Definition:Alternating current is that which is produced by a voltage source whose polarity keeps on reversing with time.

Explanation: Suppose a terminal 'A' of the alternating current source is positive and a terminal 'B' of same A.C source is negative, so during a time interval 0 to T/2. At T/2 the terminals change their polarity. Now A becomes negative with respect to B. This state continues during the time interval T/2 to T, after which terminal A becomes again positive and terminal B becomes negative, this is called one cycle. After that next cycle start and this process continues until the A.C source is providing the current. During the time 0 to T/2, it flows in one direction and during the interval T/2 - T in opposite direction. This time interval T during which the voltage source changes its polarity once is known as period T of the alternating current. Thus an alternating quantity is associated with a frequency f given by:
f = 1/T
The number of cycles passes in one second is called frequency of Alternating Current. The frequency of Alternating Current in our homes is 50Hz.

Examples: The Appliances which are operated by AC is given by:
TV, Bulb, Tube-light etc.

Sources of Alternating Current:
Alternating Current Generator

Direct Current (DC):
Definition:A current which do not changes its polarity with time is called Direct Current.

Explanation:Suppose a terminal 'A' of Direct Current Source is positive and terminal 'B' which is negative, after time interval 0 to T/2 the terminals will not change their polarity and also remain same after time interval T/2 to T. This type of current is called Direct Current.

Expampes: The DC operated objects are:
DC Motor
LED (Light Emitting Diode) etc.

Sources: The sources of Direct Current are given by
1) Dry Cell Battery
2) Solar Cell
3) Led Battery (Car Battery)

Conversion of Alternating Current to Direct Current:
The Alternating Current can be converted into Direct Current by using Diode. The current can only pass through a diode during the positive half-cycle of Alternating Current, so in this way we can convert AC current to DC Current.

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