## Key Takeaways

- Resistance is the opposition to direct current (DC) flows in a circuit caused by materials’ innate resistance to electron flow.
- Reactance is the opposition to the flow of alternating current (AC) in a circuit arising from inductive and capacitive elements.
- Resistance dissipates electrical energy as heat, while reactance stores and releases energy, causing a phase shift between current and voltage.

**What is Resistance?**

Resistance is interference in the path of flowing current through a circuit. When a specific potential is given to any circuit, then current flows in proportion to the voltage applied in the circuit. Despite this, in a circuit, there remains a small amount of hindrance in the current flowing. And this opposition is what Resistance is.

It is the property that is contained by resistors in a circuit. Therefore, in other words, resistance is defined as the ratio of the applied voltage and the current flowing in a circuit having a resistor as a load. It can also be represented through the following expression:

R = V/I

Here, R = resistance

V = voltage applied

I = current flowing in a circuit

It is measured in ohms and is denoted by R, as shown in the above equation. A circuit’s resistance depends on the conductor’s temperature, resistivity, and dimensions.

**What is Reactance?**

Reactance is the interference in the path of alternating or direct current in the circuit. The reactance of a circuit is the opposition experienced in the flow of varying currents. Reactance can be denoted by the capital ‘X.’ It also adds up in the imaginary part of the impedance value.

The main reason for reactance in a circuit is the presence of a capacitor or inductor factor as load. Therefore, in different words, the reactance of a circuit can be defined as the ratio of the voltage given and the change in current of the circuit but with either inductor or capacitor as load.

**Difference Between Resistance and Reactance**

- Resistance is the opposition in the flowing current, whereas, on the other hand, Reactance is defined as the opposition in the varying current in the circuit by a capacitor.
- Resistance is generally denoted by capital ‘R’ whereas, on the other hand, Reactance is denoted by capital ‘X.’
- The phase difference between the current and the voltage is zero, which is why it is 0 degrees for resistance, whereas, on the other hand, the phase difference between the current and the voltage is 90 degrees for reactance.
- Resistance is associated with both alternating and direct current properties, whereas, on the other hand, reactance is associated with only alternating circuits.
- Resistance is generated by only pure resistors, whereas, on the other hand, an ideal capacitor or inductor gives rise to the reactance.
- In a resistance circuit, the power supplied gets diminished in the form of heat, whereas, on the other hand, in an inductive or capacitor circuit, some of the power gets retained.
- The resistance depends on the temperature of the conductor, resistivity, and dimensions, whereas, on the other hand, reactance depends on the regularity of alternating current.

**Comparison Between Resistance and Reactance**

Parameter of Comparison | Resistance | Reactance |
---|---|---|

Definition | The opposition in the flowing current | The opposition in the varying current in a circuit by capacitor |

Denoted | R | X |

The phase difference between V and I | 0 degree | 90 degrees |

Circuit Type | Direct Current and Alternating Current Circuit | Only for AC circuit |

Circuit Element | Resistor | Ideal capacitor or inductor |

Electric Power | The power ultimately finishes in the form of heat | Some of the power gets stored in this |

Depends on | The temperature of the conductor, resistivity, and dimensions | Regularity of alternating current |

**References**

- https://www.sciencedirect.com/science/article/abs/pii/S0012369215399785
- https://www.tandfonline.com/doi/full/10.3402/ecrj.v2.28667

Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.