What do you understand by the terms 'direct current' and 'alternating current'?

Hi, I have a question and I hope anyone could answer it:

1. What do you understand by the terms ‘direct current’ and ‘alternating current’?
2. Name some sources of direct current and some of alternating current.
3. State an important advantage of alternating current over direct current.
4. What is the frequency of A.C. supply in India?

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1. (a) An electric current that reverses its direction many times a second at regular intervals is called alternating current, and it is typically used in power supplies.
An electric current flowing in one direction only, is Direct Current.

(b) Sources:
Direct Current: It is produced from sources such as batteries, power supplies, solar cells, thermocouples or dynamos.
Alternating Current:
Alternating Current: AC generators, power plants, etc., produce alternating current.

(c) Advantages of AC over DC
The major advantage that AC electricity has over DC electricity is that AC voltages can be readily transformed to higher or lower voltage levels, while it is difficult to do that with DC voltages. Since high voltages are more efficient for sending electricity great distances, AC electricity has an advantage over DC
Regulation of AC is easier without much wastage of electrical energy.
AC can be transmitted over long distances at small loss of power.

(d)In India, the AC changes its direction 100 times in one second. Hence the frequency is 50 Hz, because frequency is how many times “a maxima and a minima” cross a given point in a second.