Definition and Function of Resistors

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Resistor is? Here’s a Complete Review of Resistor Definition,  Images, Symbols, and Functions in Electronic Circuits

Electronic devices use a variety of components from simple to complex. One that must be in electronic circuits is resistors or resistance.

You may be curious why a current should be inhibited. Other components such as transistors, ICs, or diodes require precise electricity. Although the entry is appropriate from the beginning, each component still requires a specific current.

When it is inhibited, there are other components that actually require more current. A resistor is then added to increase the voltage.

Definition of Resistors


In general, the definition of resistors is electronic components with certain materials and configurations that are able to inhibit voltage and electric current. Resistors are denoted by the letter R with the unit being Ohm (Ω).

While the definition  of resistors according to mentioned that resistors are electronic components that are in charge of limiting current and managing voltage. Another name for resistors is  ‘Resistance’.

Based on Ohm’s law, it is stated that the resistance value on a resistor always has a number that is inversely proportional to the amount of electric current flowing through it.

All values in resistor elements are very important to know by electronic device designers, from there all resistor manufacturers always include these values in the resistor packaging.

To install a resistor, you need to understand its resistance value. In those components, this value is created with the resistor’s color code.

Resistor Characteristics


  • Installation / Installation

In general, resistors known to many people are small components and installed separately from other components. However, resistors are also present in ICs, transistors, transformers, batteries, capacitors, and cables.

Copper material used as electrical cables also has obstacles. Because the value is small, electricity can flow easily. Resistors in other electrical components are called internal types.

The calculation is sometimes overlooked because it does not significantly affect electrical resistance or voltage. In contrast, external types such as metal oxides are deliberately prepared to provide resistance.

  • Design Specifications

In  high-frequency electronic circuits,  such as in radio electronic components, capacitance and parasitic inductance can cause undesirable effects.

Foil resistors generally have low parasitic reactance, while wirewound resistors are among the worst types of resistors. For accurate use such as audio amplifiers, resistor electrical noise should be minimized as low as possible.

This is often specified as microvolt noise per volt of applied voltage, for a bandwidth of 1 MHz. For high power usage, power ratings are very important. It determines the maximum operating power that the component can handle without causing damage.

  • Resistance Value

The tolerance value of the resistor is also important to know before installing. When used, the component will experience a decrease in capability so that the resistance value given is no longer the same as when it was just installed. Tolerances use a certain percentage that gives the maximum limit of resistance efficiency.

Resistor Symbol


In electronic circuits, you will find resistors easily. This is because the resistor symbol is distinctive and unique.

This symbol consists of two types, namely a rectangular shape and then with two wires on the right and left and additional strikethrough lines and the appearance of sharp serrations.

Resistor components have unique color rings such as red, white, yellow, and others. This is a sign to indicate the capacity and resistance value.

The power capacity of the resistor is also very important because it determines the maximum acceptable power. If it is excessive, the resistor does not work and can be damaged.

Resistor Formula :

R = V/II = V/R and V = I.R
Where :
R =  Resistance with Ohm
units V =  Voltage with Volt unitsI = Current with Ampere units

Resistor Function


In electronic circuits, the function of resistors is to regulate the electric current in electronic circuits, such as dividing voltage, stopping transmission lines, reducing / limiting current flow, adjusting signal levels, and also refracting active elements.

Resistors generally provide the necessary bias to vital active parts of electronic circuits such as transistors and ICs. In addition to these main functions, resistors also have other functions, including:

  • Preventing Short Circuit

When we turn on electrical switches, sometimes dangerous voltage surges arise to electronic circuits and risk damaging important components.

Here resistors function to prevent these dangers. Installing resistors using series circuits with supply terminals will help check for sudden voltage increases and prevent possible danger.

  • Current Limiter

The second function of the resistor is as an LED current limiter. The term resistance is used because the way this component works does inhibit the incoming current and voltage. In general, the goal is to limit the current so that it does not excess.

Just like transistors, LEDs are also very sensitive to high-voltage currents. A resistor, when placed in series with an LED, will regulate the proper flow of current through it.

  • Electric Current Regulator

In accordance with the first function, resistors play a central role in regulating voltage and current. Components must obtain a current supply with a certain level which is sometimes very small in difference from other components.

  • Lowering the Mains Voltage

Another function is to lower the mains voltage. If the voltage is still pure, for example, directly from PLN. Power tools and cables will be overload free. The risk is the danger of short circuit and burn. The role of the resistor here is to reduce the voltage.

  • Dividing the mains voltage

The function of resistors in addition to being able to lower the electric voltage can also divide the voltage. When it is felt that the voltage is too high, the resistor can play a role in dividing the electric voltage. So, the voltage is regulated in such a way with the help of resistors.

Types of Resistors


Another type of resistor is based on a resistance value that uses Ohm units. There are two types of fixed and non-fixed resistors. An explanation of this can be seen in the following list.

Read also Definiton of Evaporator and function

Fixed Resistor:

Types of resistors consist of various types based on the resistance value and the material of manufacture. Fixed resistors use resistance that does not change because it has been determined from the beginning. Examples are charcoal and metal oxide resistors.

You see the circumference of the color ring indicating that resistance value. This type is mounted directly on the electrical circuit and does not work alone. Among the kinds of fixed resistors are:

  • Wire Resistors

Wire Resistors use iron wire as the main material. To determine the value of resistance, you need to measure the length of such wire. This is a type of resistor that is easy to find.

  • Carbon Resistors

Charcoal Resistor (Carbon Resistor) is a component made from charcoal or carbon. This component consists of several variations based on capacity. Because it is made from carbon, the resistance value can be increased even though the size is small.

  • Metal Film Resistors

Metal Film Resistors are barriers that use metal oxides. Physically, the shape and size are similar to the charcoal version. However, the material is more solid and able to provide stable voltage.

  • Ceramic Resistors

For this type of resistor, the components have a thin layer of glass on the surface. It has a characteristic small shape with a high resistance value.

Generally, ceramic resistors have a power of 1/4 watt, 1/2 watt, 1 watt, and 2 watt. But there are also those who have more power sold in the market.

Variable Resistor:

As written in the name that what is meant by variable resistors is a resistor that has a resistance value that is not fixed or can change change.

Variable Resistor is a type that can change the resistance value. Another distinctive feature lies in the value of the resistance which can change according to the reference used. You can see the variant of resistors not fixed below:

  • Potentiometer

A potentiometer is a type of variable resistor that has three terminals with a non-fixed resistance value. Potentiometers use special levers to raise and lower the resistance value.

How to change the hold value you can do by sliding (for sliding type potentios) or turning (for rotary type potentios) the existing lever.

  • LDR (Light Depending Resistor)

LDR is a type of resistor that has a special light-sensitive character (photoresistor). The resistance value in this type of resistor will decrease if there is an increase in light intensity.

  • Trimpot (Resistor Preset)

A trimpot is a type of non-fixed resistor (potentiometer) whose resistance value can be changed using a trim screwdriver (trim process).

  • Varistor (VDR)

Varistor or often known as VDR (Voltage Dependent Resistor) is a non-fixed resistor whose value changes based on the amount of voltage received.

The greater the voltage received, the value on the varistor will also be greater. And vice versa. Generally, this VDR resistor is used for voltage current stabilizer.

  • Rheostat

Rheostat is a varible resistor that can be operated under high current and voltage conditions. The components on this Rheostat consist of recitive wire windings.

How to change the value on Rheostat you can do by swiping the sweeper that moves over the Toroid.

  • Thermistor PTC (Positif Temperature Control)

PTC resistors are resistors that have resistance values based on existing temperatures. If the temperature gets colder then the PTC resistor value will be very low, on the contrary the value will rise high if the temperature becomes hot.

  • Thermistor NTC (Negative Temperature Control)

NTC resistors are thermistors whose resistance value is also influenced by the surrounding temperature. This resistor has properties that are inversely proportional to PTC resistors.

If the temperature decreases (cold), then the resistance value of the NTC resistor will rise high, and vice versa if the temperature is good (hot) then the value of the NTC resistor will decrease.

From the explanation above, you know resistors are a component that must exist. A crucial function so that other components receive electricity as needed. Without resistance, electronic devices are actually dangerous when used.


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