Concept of AC Circuit and DC Circuit


There are two ways for the flow of electric current; that is, alternating current (AC) and direct current (DC). The current keeps switching directions forward and backwards, or periodically in alternating current. While in the direct current, the flow is steady and in a single direction. 

The direction of the flow of electrons is the major difference between AC and DC circuits. 

What is an Alternating Current (AC)?

The flow of electric charges changes its direction periodically in alternating current. Most preferred, and the most commonly used electric power, is AC for household devices, buildings and offices etc. The AC current was first tested using a Dynamo Electric Generator, based on the principles of Michael Faraday. 

A waveform termed a sine wave is used to identify alternating currents. In other words, it can be referred to as the curved line. The curved lines are measured per second, which signifies electric cycles. Hertz or Hz is used to read the measurement. AC circuit are used in powerhouses, domestic and commercial buildings etc., because it’s relatively easy to generate and transport AC across long distances. Electric motors, which are used on refrigerators, and many other bigger high power appliances, are powered by alternating current.

So, an electrical current that repeatedly reverses its direction and fluctuates its value constantly with time is known as alternating current (AC), opposite to DC current, which travels in a single direction only. The sinusoidal voltage and current have been used in homes and power businesses for many decades.

Types of AC Circuit

Different variations of AC circuits are-

  • AC circuits with only resistance (R)
  • AC circuits with only inductance (L) 
  • AC circuits with only capacitance (C) 
  • AC circuits with the combination of RL 
  • AC circuits with the combination of RC 
  • AC circuits with the combination of LC
  • AC circuits with the combination of RLC

(RC) Resistor Capacitor AC Circuit

The RC circuit consists of a resistor, an AC generator, and a capacitor. A capacitor is basically an assembly of conducting plates separated by an insulator. Thus, through a capacitor, a stable current cannot flow. A time-varying electric current can add or subtract electrical charges from the plates of the capacitor.

(RL) Resistor Inductor AC Circuit

The RL circuit consists of a resistor, an AC generator, and an inductor. A back EMF is produced in the inductor coil when the circuit switch is triggered in an RL AC circuit.

To achieve its peak value, the current takes some time. The inductive time constant is the term used for the time constant.

(R) Resistive AC Circuit

Resistors regulate and enforce a voltage cut in a circuit; it also hinders and establishes the current movement in a fixed path. Resistors have an impedance identified as Resistance (R). A resistor has a resistive value that is calculated in ohm Ω. It can be calculated by using potentiometers or by using a resistor of a pre-known value.

(RLC) Resistor Inductor Capacitor AC Circuit

An AC circuit that consists of an inductor L, resistor R and a capacitor C, linked in a series or parallel, is known as an RLC AC circuit.

These components have a phase relationship that can be specified as follows:

  • The instantaneous current is in phase with the instantaneous voltage over the resistor.
  • The instantaneous current is derived by the instantaneous voltage over the inductor by 90 degrees.
  • Across the capacitor, the instantaneous voltage falls behind the instantaneous current.

Each voltage cannot be simply summed up in AC circuits, because the voltages over the various components are not in phase.

What is Direct Current (DC)?

The unidirectional propagation of electric charges results in the production of a current, which is termed direct current. Direct current is generally used in solar cells and batteries. DC current was invented by Thomas Edison, which allowed him to power several composite electrical arrangements.

Some examples are the batteries of mobile, electric vehicles, flashlights etc. DC has a dotted line or a straight-line, for representing the plus and minus signs.

Everything that runs on a battery, that is DC current, requires an AC adapter or USB cable for power transmission.

Types of DC Circuit

Since the electrical circuits can be classified into three groups, i.e. series, parallel and series-parallel, there are three categories in which DC circuit can be divided: 

  • Series DC circuit
  • Parallel DC circuit
  • Series and parallel DC circuit

Series DC Circuit

A series circuit is a circuit in which the devices are connected end-to-end. In series DC circuits, a linear path for flowing current is created by connecting the resistive elements in an end-to-end way.

Parallel DC Circuit

When one end of an individual element is linked to a mutual point, and the other end is linked to a different mutual point in the arrangement of multiple electric components, then such connection is known as a parallel circuit. 

An equal voltage drop will be there over all the components, and it will be equal to the voltage between the two mutual joints, where the components are linked.

Series and Parallel DC Circuit

Electrical circuits are generally a grouping of both parallel and series DC circuits. Using Ohm’s Law and rules for parallel and series DC circuits, these complex circuits are solved.

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