DC Circuit Theory: Relationship between Voltage Current and Resistance

Have you heard about DC circuit before? Especially for those who work in electricity sector or learning electronics, it sounds familiar with this term. While it goes to run the DC electricity, it should be completed by applying a DC circuit. Hence, A DC circuit will be an essential thing in this case.

DC circuits as it is used and known in electrical application, can be applied in series, parallel, or combination of each. However, if you’re learning about the electricity especially AC circuits for home electrical utilization, it will also be important to understanding DC circuit as well.

1. Simple Introduction of DC Circuit

The existence of DC circuit has been increasing in modern life. Nowadays, life may seem difficult to running well if it were not any both electricity and electronics utilization. Began from more than past thousand years, the history of electricity was pioneered by the Greek philosopher Thales.

Since then, Thales became the earliest researcher who known in the study of electricity. But nowadays, people may seem familiar with Alessandro Volta who had invented the battery as the most common DC power source. That’s why it’s officially known the unit Volt due to Volta’s source invention.

So, what is actually DC current? Direct current or mostly recognized as a DC can be described as the particles of charging flow that works in only one unchanging direction. It’s generally established as an electron that flowing through any conductive material.

2. Let’s Start from the Definition of DC Circuit

Feel so hard to understand which kind of thing DC current is applied? Just look around in every corner of your home. There you may find any electronic devices which supplied by the DC current. Compared to AC current that supported by power stations, a DC current is more practical.

DC current can be easily found in any side of your home. For many consumer devices, DC looks common so it’s easy to apply in any electronic devices. Some of devices that supplied by Direct Current are battery, car, television, computer, phone, lightning, or even the calculator you’re usually using every day.

After knowing direct current, now let’s move to the definition of DC circuit. DC circuit can be explained as the closed path in which the direct current flows. The current of the DC circuit is flowing just in one direction. Hence, it’s mostly found in any low voltage applications with the main component is resistor.

Resistor Symbols

3. Understanding the DC Circuit Theory

Formerly, the materials we can found presently are made up from atoms. Atoms itself is consisting of neutron, proton, and electron. Basically, protons consist of positive electrical charge meanwhile neutrons don’t consist of electrical charge which means that neutrons are definitely neutral.

In other hand, electrons are consisting of a negative electrical charge. Due to difference of charge they have, and powerful forces of attraction that exists between both nucleus and the electrons that can be found in outer shell, atoms are basically bound together.

Only when protons, neutrons and electrons are united, the atoms will essentially stable. Otherwise, when protons, neutrons and electrons are separated one another, all those elements will reform and begin to maintain a potential of attraction. This chemical reaction is commonly known as a potential difference.

According to DC circuit theory, the flow of electrons can be named as an electrical current. Theoretically, as the material that moves through makes a restriction to the flowing electron, the electrons itself don’t flow freely through the circuit. The restriction that just happens is called resistance.

Basically, all the electrical or electronic circuits are separated into three which are Voltage (v), Current (i), and Resistance (Ω). Then, let’s check all the laws relate to DC circuit theory in the applications of direct current:

1. Ohm’s law

As the Ohm’s law mentioned, the current in a circuit will be proportional to the potential difference across the circuit straightaway. Further, it will also be inversely proportional to the resistance happens in the circuit. In the applications, the Ohm’s law is commonly implemented to any circuits or individual part of it.

Kirchoff’s node rule

In the Kirchoff’s node rule, all currents at a node or generally called junction point have an algebraic sum which is zero. Technically, the currents that come to a node can be considered negative while currents that leaving a node will be considered positive.

As well as there is no charge can be stored at a node and neither charge be created nor destroyed at the node, the total current come in a node should equal the total current that leaving the node. Due to that condition, the Kirchoff’s node rule is also known as the low of conservation of charge.

Kirchoff’s loop rule

Looks different from the Kirchoff’s node rule, the Kirchoff’s loop rule mentions that algebraic sum of all the changes in potential or voltages that found around a loop should equal zero. Practically, as long as the potential is increasing low in the current flow direction, a potential difference is viewed negative.

4. Let’s Find Out the Concept of Current, Voltage, Resistance, and Power

Before begin to understand the Direct Current/DC circuit, it’s essential to define what actually Current, Voltage, Resistance, and Power are. Current can be explained as the flow of electrons which exists inside the circuit.

Voltage Symbols

The current is theoretically defined in Amperes as per SI unit with the denotation I or i. 1 Ampere means there is a quantity of electricity conducted in one second. As well as you make out a scenario to practice, as it occurs in the power supply, the electrons will slightly flow from the negative to the positive.

In other hand, there is a potential difference of two points found in a circuit and it’s commonly called Voltage. Voltage will recognize an electrical charge from the potential energy stored in an electrical supply point. That difference found can be seen as a voltage drop or known as a potential difference.

The Voltage drop furthermore is also known as a potential difference. It is commonly measured in Volts with V or v symbol. If it looks over capacity on the charge, it means there is more voltage.

Similar to the Current and Voltage, the Resistance can only be defined in positive value, not the negative. The resistance will notify the materials found in any passing current and recognize it as a good conductor or band conductor. Good conductor means it has low resistance and vice versa.

5. What is Direct Current?

As we learned before when we were in elementary school, everything you found is made by atoms. Atoms itself are consisting of three particles i.e. Electrons, Protons, and Neutrons. Theoretically, Neutrons have no any charge meanwhile Protons can be positive and Electron can be negative.

In case of Direct Current, The flow of current is possibly varying with time whereas the polarity will not reverse and changed with respect to time. Meanwhile, there is no perfect condition factually, especially in the case of circuit where electrons flow.

As long as the conducting materials seem not perfect to let the electrons freely flow, all those electrons are not independently flowing. If we’re looking to a certain rule of restrictions, it’s truly contradicting the flow of electron.

Whether it’s electronic or electrical circuit, there must be comprising of three quantities especially for this issue. All those basic individual quantities are:

  • Voltage (V)
  • Current (I)
  • And Resistance (R)

All those three elements will be fundamentally basic quantities. Those quantities come along in almost cases when we are learning about something related with Electronics or Electrical.

6. Relations between Voltage, Current and Resistance in DC Circuit

Now we can conclude that Voltage, Current, and Resistance are related one another. The relationship between those elements also creates the basis of Ohm’s law. Down below are some essential points included in a basic summary of Voltage, Current, and Resistance.

A basic summary of the three units is given below.

  • Voltage also known as potential difference can be described as the measure of potential energy. It is commonly also known as “volt drop” because it happens between two points in a circuit.
  • When it comes to connecting a closed loop circuit, there will be a current flows around the circuit that produced by voltage.
  • In case of DC voltage, the symbols +ve as positive and –ve as negative are generally used to refer the polarity of voltage supply.
  • Voltage consists of the symbol V for voltage and E for electrical energy as it is measured in Volts.
  • Current flow can be explained as the combination of the flow of electron and holes through a circuit.
  • The continuous flow of charge that measured in Amperes with I symbol, is theoretically named current.
  • Current is also proportional to voltage as it’s explained in the formula ( I ∝ V )
  • Resistance can be explained as the opposition to current that flows around a circuit.
  • Resistance with low values means it is a conductor whereas resistance with high values means it will be an insulator.
  • Those which are inversely proportional to resistance can be called current as it’s explained in (I1/∝ R).
  • Resistance is explained with Greek symbol Ω or the letter R and measured in Ohms (Ω).

7. How Exactly Electron Flow Occurs?

Theoretically, the electron flows around the circuit by inversing the direction of the conventional current flow. Hence, it will current from negative to positive. The actual current flow in an electrical circuit formed by electrons occurs in battery. It flows from negative pole of the cathode then return to the anode.

The scheme of the flows occurs due to the charge on electron is negative, thus it will be tied up to the positive terminal. The scheme of this flow can be described as an Electron Current Flow. From this scheme, now we can conclude that the electrons will flow from the negative to the positive terminal.

This is because the charge on an electron is negative by definition and so is attracted to the positive terminal. This flow of electrons is called Electron Current Flow. Therefore, electrons actually flow around a circuit from the negative terminal to the positive.

8. What Makes a Conventional Current Flow Difference to Electron Flow?

The flow of current that occurring from negative to positive is commonly called a conventional current flow. It’s conventionally explained as the flow of positive charge runs around the circuit which turning from positive to negative.

The direction of electric current was formerly recognized that it flown in circuit. Since then, the conventional current flow was historically explained as a convention which chosen when electricity was discovered. It furthermore gave the flow of electrical current which runs from positive to negative.

Due to the scheme which shows how conventional current flow occurs, it can be concluded that conventional current flow was actually the opposite of the actual flow of electrons due to its electrical current direction.

9. Types of DC Circuit

Now, after understanding the component of DC current, it’s time to move to the types of DC circuit. The electrical DC circuit is primarily classified into three categories which are the parallel DC circuit, series DC circuit, and Series & parallel DC circuit. Here below is the explanation of each group:

1. DC Series Circuit

The DC series circuit can be explained as the circuit that that supplied by DC series source with connected end to end resistors. In this type of circuit, if there conduct a trial, all the lamp will be controlled by the single switch which means it can’t be controlled individually.

DC series circuit is commonly applied in any decoration purpose that demands low voltage lamps that connected in series. Some electric devices such as light bulbs can also be planted in series in the circuit. Light bulbs for instance can be placed in the poles of the battery in positive and negative.

Commonly, a series circuit is also called voltage divider. It’s based on the ability to divide the total voltage into fractional portions of constant ratio through the series circuit.

2. DC Parallel Circuit

The DC parallel circuit is the circuit that supplied by DC source. On DC parallel circuit, the current flow through the resistors that one end and another end are joined to a common point. Some of electrical devices can be arranged in any parallel configuration such as the holiday lighting.

Parallel circuit is commonly used for any application such as holiday lighting and the electric wiring applied in home. By applying the DC parallel circuit, the lights or appliances can only be both turned on and off as it’s needed. Once the light is turned out or burned out, all the light would go off as well.

You can also put or replace other bulbs from parallel circuits being in series due to many possibilities to combine each.

3. DC Series-Parallel Circuit

The DC series-parallel circuit is the configuration of both the series and parallel circuit which are connected one another.

10.  What Makes an Alternating Current (AC) and Direct Current (DC) Looks Different?

In a simple way, we can say that current flowing in a single direction can be called Direct Current or DC. Meanwhile, the current alternating back through the circuit can be called Alternating Current or AC. Both DC and AC only flow through a circuit as the voltage source is connected to it.

Direct current may look little different to Alternating current. The electric current flows only in one direction as it comes to direct current (DC). On the other hand, in an Alternating current (AC), the electric current will periodically change the direction and the voltage will also reverses due to this scheme.

11. Application of Direct Current (DC)

Not only understanding the theory about Direct Current/DC circuit that looks important, know the application of Direct Current (DC) is also essential. Mostly devices relate to electronics that you found or even build will utilize Direct Current (DC).

Because it’s really simple to understand and use, a Direct Current itself is mostly chosen than Alternating Current. It’s because the DC supplies a voltage or current constantly. Due to the current that flows only in one direction, the Direct Current is specified as the unidirectional flow of current.

Voltage or current sometimes is possibly to changing overtime due to the direction of flow that is not changing. For instance, sometimes we find a battery slowly lose the charge. It defines that as the battery has been used, the voltage dramatically drops. There’s conclusion about the constant of the voltage.

So what’s exactly the device that supplied by direct current (DC)? It’s clearly easy to find out the answer. All the electronics devices and parts we can find around or we can buy anywhere we want are running on Direct Current. The electronic devices that run on DC such as cellphones, Flat-screen TVs, Flashlights, and also the modern one is a Hybrid or electric vehicles.

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