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Why Do We Use Resistors in Circuits and Why Is It Important?

We use resistors to control the flow of electricity in a circuit. Resistance is the ability to impend the flow of electricity. Resistors are made of carbon or metals like copper, nickel, and zinc which make it difficult for electricity to flow past the resistor.

The carbon resistor is the most common among the two as it is used in low current circuits across various applications.

Resistors are part of any electrical circuit, whether the air conditioner, LED lights, dishwasher, or your computers. To control the flow of electricity, they are built into other circuits. This helps circuits work as a whole even when components consume different amounts of current.

Why Do You Use Resistors in Circuits?

To Protect the Circuit Against Voltage Spikes

Resistors act as control points to protect your components from voltage spikes. Sudden power spikes may damage some components sensitive to high electrical current in the circuit. In this case, the resistor acts as a circuit breaker and stops the high current from moving to the other parts of the circuit. These resistors are used in fuses and circuit breakers.

Ensure that Components Receive Proper Voltage

Each component in the circuit uses a specific voltage to run efficiently. However, it is not easy to vary voltages for each component in the circuit. The resistors can be rated for a specific voltage required by the component next to them.

These resistors slow down or drop the voltage to the specific one required by the component. Therefore, the circuit is able to use a standard voltage and still get a specific current for each component.

One of the ways you can use these resistors is when you want to change your lighting from incandescent turn signals to LED. Each light has an LED load resistor that ensures the turn signal blinks properly and at the right speed.

Types of Resistors

There are two types of resistors on the market that serve distinct roles in a circuit. A circuit may have both at different points.

Fixed Resistors

These are the most common types of resistors in applications. They are used to control the flow of current up to a specific value that will not be changed as the circuit runs.

The values of the current are calculated and set during the design phase of the electronic device. Here are common fixed resistors.

Carbon Composition

Carbon composition resistors are formed by mixing carbon granules and a binder into a small rod. These resistors are not used these days due to their large negative temperature coefficient and age rather fast.

Some variants include a carbon film resistor that uses a carbon film set onto a ceramic former.

Metal Oxide Film Resistor

This is the most common type of resistor. It uses a metal oxide film instead of carbon. The metal oxide is then deposited on a ceramic rod. Then, the rod is covered with an epoxy coating. It has superior performance to any carbon-based resistor.

There are variants on the market, such as the metal film resistor, which uses a metal film rather than an oxide and has a similar performance.

Variable Resistors

These resistors consist of a fixed resistor and a slide that taps on the element. It has two connections to the fixed element and a slider that determines the current that will pass through the resistor.

The user varies the resistance by turning the slider via a knob. These resistors are used in many different applications, like radio volume controls and sliders in professional audio mixers.

Variable resistors are essentially fixed resistors with a slider that varies touches on different sections to vary the amount of current that passes through. Therefore, any resistors discussed above can be used with a few modifications.

Other Types of Resistors

There are other types of resistors on the market that include the following:

A Light Dependent Resistor

These resistors are called photoresistors, and they change their resistance with the light level. They are used in light sensors in various applications like security lights and remote controls.


These are heat-sensitive resistors. Their resistance increases with the increase in heat or vice versa. They are used in heat controls in HVACs, ovens, and air conditioning systems. Common types include NTC and PTC thermistors.


Resistors are important in circuits for the following reasons:

  • They ensure that the components receive the right voltage.
  • They prevent damage to components due to power spikes.

There are various types of resistors. They include:

  • Variable resistor
  • Fixed resistors
  • Light-sensitive resistors
  • Thermistors

Each of these types has a specific application different from the others. Several components may fail to function without resistors, and sensors may fail to respond to changes in predetermined conditions.

All electrical circuits, whether with controls or not, use resistors to accomplish the set tasks. New technologies have made resistors smaller and more effective for use in small circuits.