What are the Differences Between Impedance and Resistance?

Impedance and resistance are two important electrical properties encountered in electrical circuits, but they differ in their functions and effects. Resistance refers to the ability of a circuit element to resist electric current, while impedance is considered the combination of both resistance and reactance (inductance and capacitance).

While resistance causes energy loss by converting the energy of the electric current into heat, impedance includes the effect of reactive components (inductance and capacitance) along with resistance depending on the frequency of the current. Therefore, the main difference between impedance and resistance is that impedance is a concept valid in AC (alternating current) circuits whereas resistance functions the same in DC (direct current) and AC circuits whereas impedance can vary in frequency. In this article, we will examine the differences between impedance and resistance in more detail.

Impedance and Resistance Concepts

Impedance and resistance are two important electrical terms that describe the basic characteristics of electrical circuits. Both describe the behavior of electric current, but they emphasize different aspects:


Impedance is a concept that combines the resistance and reactance (inductance and capacitance) of an electrical circuit in AC (alternating current) conditions.

Impedance both expresses the AC equivalent of resistance, that is, represents resistive losses, and takes into account reactive components. Reactive components are associated with the phase angle difference of current and voltage waves.

Impedance is measured in ohms (Ω) and is used to describe the complexity and frequency-dependent behavior of AC circuits.


Resistance measures the ability of substances or components in an electrical circuit to resist electric current.

The resistance of a circuit element is inversely proportional to the conductivity of that element. In other words, an element with higher resistance allows less electric current.

The resistor converts the energy of the electric current into heat, converting this energy into loss. Therefore, energy loss occurs in a resistive circuit.

Resistance is measured in ohms (Ω) and is also valid in DC (direct current) circuits.

In summary, while resistance is a concept that is effective in DC circuits, impedance is used as a more comprehensive indicator in AC circuits. Resistance represents only energy loss, while impedance takes into account both energy loss and phase shift. Therefore, in the analysis and design of electrical circuits, the concept of impedance plays an important role in AC circuits.

Key Differences Between Impedance and Resistance

Impedance and resistance are two fundamental concepts that describe electrical behavior, but there are some key differences between them:

Current Type:

Resistance is generally effective in DC (direct current) circuits. A resistive element resists DC current and the direction of the current does not change.

Impedance is more important in AC circuits. Impedance addresses situations where AC current varies in frequency. The change of AC current in frequency shows the effect of reactive components.

Unit of Measurement:

Resistance is measured in ohms (Ω).

Impedance is also measured in ohms (Ω) because it includes both resistance and reactance.

Energy Loss:

Resistance is a factor that causes energy loss. When an electric current passes through a resistive component, heat is produced and energy is lost.

Impedance also refers to energy dissipation but describes a more complex energy distribution by considering the phase angle of the reactive components.

Practical Applications Between Impedance and Resistance

Impedance and resistance are two important concepts for understanding different aspects of electrical circuits and using them in engineering applications. Here are some examples of how impedance and resistances are used in practical applications:

Resistance Applications:

  1. Electrical Heating: Resistors are used as heating elements. For example, electric stoves, ranges, and water heaters use resistors.
  2. Signal Regulation: Resistors are used to regulate signals in electronic circuits. For example, a resistor can be used to adjust the signal level at the input of an amplifier.
  3. Voltage Division: Resistors are used in voltage division circuits. This is used to reduce or divide a voltage by a certain percentage to provide a suitable voltage to another device.

Impedance Applications:

  1. AC Circuits: Impedance plays a critical role in the analysis and design of AC circuits. Impedance calculations are used especially in complex AC circuits such as resonant circuits and filters.
  2. Speakers and Microphones: In audio equipment, speakers and microphones are designed based on the concept of impedance. Impedance matching ensures that audio signals are transmitted correctly.
  3. Electrocardiography (ECG): In medical applications, impedance is used to measure heartbeats. Impedance measurements are made to analyse the interaction of ECG electrodes with the skin.
  4. Electromagnetic Compatibility (EMC): To ensure EMC compatibility of electronic devices, the impedance of the circuits is taken into account. Correct impedance matching helps reduce electromagnetic interference.
  5. Telecommunications: Impedance matching on telephone lines and data transmission lines allows signal transmission to be optimized.

Impedance and resistance are fundamental concepts in the fields of electrical and electronic engineering and are important for the design, analysis, and optimization of the performance of electrical circuits. A good understanding contributes to the development of more efficient and reliable electrical systems.

Impedance and Resistance in Electrical Circuit Design

In electrical circuit design, impedance and resistance are two fundamental concepts important for understanding and controlling the performance and behavior of circuits. Here are some important points about how the concepts of impedance and resistance are used in electrical circuit design:

  1. Impedance Usage:

Impedance plays a critical role in the analysis and design of AC (alternating current) circuits. Impedance combines resistance and reactance (inductance and capacitance) and describes the behavior of the circuit depending on the frequency of the AC current.

Impedance ensures proper matching between source and load devices in AC circuits. Impedance matching maximizes power transfer and minimizes signal loss.

  1. Resistor Usage:

Resistor is used in both DC (direct current) and AC circuits. Resistance limits the flow of electric current through a particular electrical component or circuit element.

Resistors can be used to regulate the levels of signals or for protection or load balancing of an element with a certain resistance value.

  1. Filter Design:

Impedance and resistance are used in the design of filter circuits. Filters are used to isolate or suppress certain frequency components, and impedance and resistance values are important in this design.

  1. Sound Systems:

In the design of audio systems, the impedance of the speakers and the impedance matching between the circuit elements are taken into consideration. This ensures that audio signals are transmitted correctly and prevents damage to the amplifiers or speakers.

  1. Power Distribution:

In the design of power distribution systems, resistance values determine energy losses. High resistance can increase energy losses, so it is important that power transmission lines have low resistance.

Impedance and resistance have a significant impact on the stability, reliability and efficiency of electrical circuits. Therefore, accurately designing electrical circuits and properly calculating impedance and resistance values is a fundamental skill in the fields of electrical engineering and electronic design.