What is the Difference Between AC and DC Currents

In the today’s world electricity is most important next to the oxygen in the human. When the electricity was invented many changes have taken place over the years. Dark planet turned into a planet of lights. In fact, it made life so simple in all circumstances. All the devices, industries, offices, houses, technology, computers run on electricity. Here energy will be in two forms, i.e. alternating current (AC) and direct current (DC). Regarding these currents and the difference between AC and DC will be discussed in detail, its basic function and uses of it. Its properties are also discussed in a tabular column.

Working and Difference between AC and DC

The difference between AC and DC  mainly includes the following

Difference between AC and DC
Difference between AC and DC

Alternating Current (AC)

Alternating current is defined as the flow of charge that changes direction periodically. The result obtained will be, the voltage level also reverses along with the current. Basically AC is used to deliver power to industries, houses, office buildings, etc.

AC Source
AC Source

Generation of AC

AC is produced by using called an alternator. It is designed to produce alternating current.Inside of a magnetic field, a loop of wire is spun, from which induced current will flow along the wire. Here the rotation of the wire may come from any no of means i.e. from, a steam turbine, flowing water, a wind turbine and so on. This is because the wire spins and enters into different magnetic polarity periodically, the current and voltage alternates in the wire.

Generation of AC
Generation of AC

From this, the generated current can be of many waveforms like sine, square and triangle. But in most of the cases sine wave is preferred because it is easy to generate and calculations can be done with ease. However the rest of the wave requires an additional device to covert them into respective waveforms or the shape of the equipment has to be changed and the calculations will be too difficult. Description of Sine waveform is discussed below.

Describing a Sine Wave

Generally, AC waveform can be understood easily with the help of mathematical terms. For this sine wave the three things which are required are amplitude, phase and frequency.

By looking at just voltage, sine wave can be described like the below mathematical function:

V(t) = VP Sin (2πft + Ø)

V(t): It is a function of time a voltage. This means that as time changes our voltage also changes. In the above equation the term which is right of the equal sign describes how the voltage changes over time.

VP: It is the amplitude. This states how maximum the voltage the sine wave could reach in either direction, i.e. -VP volts, +VP volts, or somewhere in between.

The function of sin( ) states that the voltage will be in the form of a periodic sine wave and will act as a smooth oscillation at 0V.

Here 2π is constant. It converts the frequency from cycles in hertz to angular frequency in radians per second.

Here f describes the sine wave frequency. This will be in the form of units per second or hertz. The frequency tells how many times a particular waveform occurs within one second.

Here t is a dependent variable. It is measured in seconds. When the time varies the waveform also varies.

The φ describes about the phase of the sine wave. Phase is defined as how the waveform is shifted with respect to time. It is measured in degrees. The periodic nature of the sine wave shifts by 360° it becomes same waveform when shifted by 0°.

For the above formula, the real time application values are added by taking United States as a reference

Root mean square (RMS) is another small concept which helps in calculating the electrical power.

V(t) = 170 Sin ( 2π60t )

The other waves, i.e. triangle and square are shown below:

RMS Sine Waveform
RMS Sine Waveform
Triangle Waveform
Triangle Waveform
Square Waveform
Square Waveform

Applications of AC

  • Home and office outlets are used AC.
  • Generating and transmission of AC power for long distances is easy.
  • Less energy is lost in electrical power transmission for high voltages (> 110kV).
  • For higher voltages imply lower currents, and for lower currents less heat is generated in the power line which is obviously due to low resistance.
  • AC can be easily converted from high voltage to low voltage and vice versa with the help of transformers.
  • AC power the electric motors.
  • It is also useful for many large appliances like refrigerators, dishwashers etc.
  • Direct Current

Direct current (DC) is the movement of electric charge carriers, i.e. electrons in a unidirectional flow. In DC the intensity of the current will vary along with time, but the direction of movement stays the same in all time. Here DC is referred to voltage whose polarity never reverses.

DC Source

In a DC circuit, electrons emerge from the minus or negative pole and move towards the plus or positive pole. Some of the physicists define DC as, it travels from plus to minus.

DC Source
DC Source

Generally the basic source of direct current is produced by batteries, electrochemical, and photovoltaic cells. But AC is most preferred across the world. In this scenario AC can be converted to DC. This will happen in multiple steps. Initially, power supply consists of a transformer, which later converted into DC with the help of a rectifier. It prevents the flow of current from reversing and a filter is used to eliminate current pulsations in the output of the rectifier. The is the phenomenon how AC is converted into DC

Example of a Recharging Battery

However, all electronic and computer hardware to function they need DC. Most of the solid-state equipment requires voltage range in between 1.5 and 13.5 volts. Current demands vary accordingly with the devices which are used. For example the range from practically zero for an electronic wristwatch, to more than 100 amperes for a radio communications power amplifier. Equipment using, a high-power radio or broadcast transmitter or television or a CRT (cathode-ray tube) display or vacuum tubes require from about 150 volts to several thousand volts DC.

Example of a Recharging Battery
Example of a Recharging Battery

The main Difference between AC and DC is discusses in the following comparision chart

           S No Alternating Current Direct Current

1

The amount of energy that can be carried  It is safe to transfer over longer city distances and will provide more power. Practically the voltage of DC cannot travel very far until it begins to lose energy.

2

The cause of the direction of flow of electrons It is denoted rotating magnet along the wire. It is denoted steady magnetism along the wire

3

Frequency The frequency of alternating current will be either 50Hz or 60Hz depending upon the country. The frequency of direct current will be zero.

4

Direction It reverses its direction while flowing in a circuit. It only flows in one direction in the circuit.

5

Current It is the current of magnitude which is varying with time It is the current of constant magnitude.

6

Flow of Electrons Here electrons will keep switching the directions – forward and backward. Electrons move steadily in one direction or ‘forward’.

7

Obtained from The source of availability is A.C Generator and mains. The source of availability is either Cell or Battery.

8

Passive Parameters It is Impedance. Only Resistance

9

Power Factor It basically Lies between 0 & 1. It will be always 1.

10

Types It will of different types like Sinusoidal, Square Trapezoidal, and Triangular. It will be of Pure and pulsating.

In this article What Is the Difference between AC and DC currents is explained in detailed. I hope that every point is understood clearly about the alternating current, direct current, waveforms, about equation, differences of AC and DC in tabular columns along with their properties. Still unable to understand any of the topics in the articles or to implement the latest electrical projects, feel free to raise a question in the comment box below.Here is a question for you, what is the power factor of an alternating current?

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6 Comments

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