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


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



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


  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



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


Question 2 Page 237 - Name some sources of direct current.

View Answer


Question 3 Page 237 - Which sources produce alternating current?

View Answer



Go Ad-free
Maninder Singh's photo - Co-founder, Teachoo

Made by

Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo