What is Direct Current
If current flows only in 1 Direction,
it is called Direct Current
It is denoted by DC or d.c
Here, the positive and negative polarity of current is fixed
Example
The current we get from a cell or a battery is direct current because it always flows in the same direction.
What is Alternating Current?
Alternating Current reverses direction in equal intervals of time
It is denoted by AC or a.c
Positive Negative Polarity is not fixed and keep on changing
Uses
It is used to transmit current over long distance without much loss of current
Most of power stations in India generate Alternating Current
Difference between Direct Current and Alternating Current
-vs-direct-current-(dc).png)
| Direct Current | Alternating Current | |
| Meaning | Current flows only in one direction |
Current reverses direction in equal intervals of time
|
| Abbreviation | D.C. | A.C. |
| Change in Polarity | There is no change in polarity. It is fixed. | There is change in polarity after a fixed interval. It is not fixed. |
| Frequency | Frequency of Direct Current is 0 | Frequency of Alternating current depends on the country - it is usually 50 Hz or 60 Hz |
| Current | Current is of constant magnitude | Current varies with time |
| Uses | Used in televisions. | Used to transmit current over long distances. |
| Component Used in Generator | Split Ring is used | Commutator is used |
What is Frequency of Alternating Current generated in India?
It is 50 Hz
It means the coil is rotated at a frequency of 50 Revolutions per second
In every revolution, it changes direction from Positive to Negative and then from Negative to Positive
Hence, overall it changes direction 100 times in 1 second (50 positive + 50 Negative)
Hence we can say that
This Alternating Current changes direction every 1/100 seconds
Explanation-
Time in which 100 directions changed = 1 second
Time in which 1 directions changed = 1/100 second
Which Type of Current is Used in Television/Radio Sets
They use Direct Current (D.C. or d.c)
Note - Power supply to television sets is in form of DC
They have a device which convert AC current into DC current
Questions
Question 2 Page 237 - Name some sources of direct current.
Question 3 Page 237 - Which sources produce alternating current?
