# Difference between Alternating Current and Direct Current

DifferencesAC & DC SupplyElectronics & Electrical

The directed flow of electrons or charge in an electric circuit is known as electric current. Based on the nature of flow of electrons (or electric current), the electric current is classified into two types: AC (Alternating Current) and DC (Direct Current). Go through this article to find out more about AC and DC and how they are different from each other.

## What is Alternating Current?

AC stands for Alternating Current. The type of electric current whose magnitude changes continuously and direction changes periodically is known as alternating current or AC. In practice, the alternating current is produced by alternating voltage source such as alternator or AC generator, etc. The waveform of alternating current (AC) is shown in Figure-1. In case of AC, the total amount of time taken by a waveform of alternating current to itself is known as time period of the AC waveform. The rate at which the waveform repeats itself, i.e. the number of cycle complete in one second, is known as frequency of the AC waveform. The relation between frequency and time period of an AC waveform is given by the following expression.

$$f=\frac{1}{T}$$

There are different types of AC waveforms like sinusoidal AC, square wave, triangular wave, etc. The AC is widely used in our day to day life such as to run fan, bulb, AC, washing machine, etc.

## What is Direct Current?

DC stands for Direct Current. The type of electric current whose magnitude does not change with the time and flows only in one direction (i.e. has unidirectional flow) is known as direct current or DC. Therefore, DC has a constant magnitude and direction. Consequently, the frequency of DC is zero. The waveform of the DC is shown in Figure-2. The DC is widely used in electronic device such as computers, mobiles, laptops, toys, etc. The DC is obtained from battery, cell, DC generators and rectifiers (by converting AC into DC).

## Difference between AC and DC

The following table highlights the key differences between alternating current and direct current −

ParameterAlternating Current (AC)Direct Current (DC)
DefinitionThe type of electric current in whose magnitude changes continuously and direction changes periodically is known as alternating current (AC).The types of electric current whose magnitude and direction does not change with time is known as direct current (DC).
Direction of flow of charge (electrons)In case of alternating current, the flow of electrons is bidirectional, i.e. electrons flow in both forward and backward direction.In case of direct current, flow of electrons takes place in only forward direction. Thus, the flow of electrons is unidirectional.
TypesAlternating current may be of various types based on the waveform such as sinusoidal, triangular, square, trapezoidal, etc.Generally, the direct current is of two types: constant DC and pulsating DC.
FrequencyAC has a specific frequency. In practice, the frequency of AC is 50 Hz or 60 Hz.The frequency of DC is zero.
MagnitudeThe magnitude of alternating current changes continuously.The direct current has a constant magnitude, i.e. it does not change with time.
Direct of current & polarityThe alternating current flows in both directions (forward and reverse), thus polarity cannot be mentioned in the circuit.The direct current always flows from positive to negative. Hence, polarity marking is possible in case of DC.