difference between ac and dc | alternating current

Students often get confused when they are asked to differentiate between alternating current and direct current. This blog covers 20 difference between ac and dc.

Electrical current flows in two ways, it either flows in single direction or reverses its direction periodically. When electrical current flows in single direction it is known as Direct Current ( DC ). The electrical current which reverses its direction periodically is known as Alternating Current ( AC ).


Direct current

Alternating current


1.      DC stands for Direct Current.

1.      AC stands for Alternating Current.

2.      DC flows in only one direction.

2.      AC reverses its direction periodically.

3.      Magnitude of current may be constant or vary with time but in only one direction.

3.      Magnitude of current vary with time.

4.      The frequency of DC is zero. It may can have high frequency ripples.

4.      The frequency of AC is 50 Hz / 60 Hz, depending upon the country. 50 Hz in India.

5.      Dc can be stored.

5.      AC cannot be stored.

6.      Voltage cannot be changed easily.  Complex circuits are required to change DC voltage.

6.      Voltage can easily be changed using transformer.

7.      Useful for low voltage/power electronic devices.

7.      Used for heavy loads like motors, lights, heating elements, etc.

8.      DC is difficult to protect from fault because of continuous supply.

8.      AC is easier to protect from fault because of frequency. It itself comes to zero on every wave.

9.      Electricity is not supplied to general consumer in DC form.

9.      Electricity is supplied to general consumer in AC form.

10.   DC is portable. It can easily be carried in the form of battery.

10.   AC is not portable.

It can be generated using a portable generator.

11.   Fuse can be used for protection but same fuse can be used for higher voltage Ac.

High efficiency fuse is needed.

11.   Fuse can be used for protection.

12.   Voltage is represented as an equation.

V = 12

For ripple Dc that is AC + DC mix

V = 12 + 6 Sin ωt

12.   Voltage is represented as sine equation.

V = 12 sin ωt

13.   DC can be generated in battery using chemical reaction.

It can also be generated by mechanical means such as generator but with some ripples.

13.   AC can be generated by mechanical means such as generator.

14.   DC can be converted into AC using inverter.

14.   AC can easily be converted into DC using rectifier.

15.   No wireless transmission in DC under analog signals.

Instead DC uses digital signal like 010101.

15.   High frequency AC ( Analog signal ) is used in wireless transmission of television, radio, etc.

16.   DC has trapezoidal, triangular and square waves but in only one direction.

It does not fluctuate polarity.

16.   AC is mostly sinusoidal.

Small signals may be trapezoidal, triangular and square, etc.

17.   DC can be Transmitted to very long distances using HVDC.

17.   AC can be transmitted to long distance but not very long distances.

18.   DC ( HVDC ) power transmission is cheap for very long distance and costly for short distance when compared to AC.

18.   AC power transmission is cheap for small distance and costly for very long distance.

19.   DC ( HVDC ) power transmission is efficient for very long distance but inefficient for very short distance when compared to AC.

19.   AC power transmission is more efficient for short distance.

20.   Two different generating stations can be connected directly using HVDC transmission.

20.   Two generating stations with different frequency cannot be connected together directly.


HVDC Transmission

High Volt Direct Current transmission is known as electrical superhighway or power superhighway that uses Direct current for bulk transmission of electrical power for very long diatances.

It is mostly used for bulk electrical transmission between two country.

Frequently Asked Questions


  1. Can we convert AC to DC and DC to AC ?
  • Yes we can convert AC to DC by using rectifiers ( Diodes ). We can also convert DC to AC. The device used to convert DC to AC is known as inverter.
  1. Where is Alternating Current and Direct Current used ?
  • Electricity is supplied to its customer in AC form. Direct current is used in low voltage applications like electronic circuits, toys, remote controls, etc.
  1. How is AC and DC generated ?
  • Alternating current is generated by AC generators that work on the principle of electromagnetic induction.
  • Direct current is either converted from alternating current through rectifiers or produced by chemical reaction in batteries.


Akash Sharma

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