reactance

/ri:'æktəns/

Thân thiện

A student measures the reactance in a simple AC circuit.

Definition

1. Noun:
   • Electrical opposition to alternating current: Reactance is the measure of opposition that an electrical component (like an inductor or capacitor) presents to the flow of alternating current (AC). Unlike resistance, which opposes both AC and direct current (DC), reactance is specific to AC circuits and varies with the frequency of the current.
   • A component of impedance: In AC circuit analysis, reactance (denoted by X) is the imaginary part of impedance (Z), which describes the total opposition to current flow.

Examples of Usage

• Noun:
  • The capacitor introduces a capacitive reactance that decreases with increasing frequency.
  • To calculate the total impedance, you must consider both the resistance and the reactance of the circuit.
  • Inductive reactance causes the current to lag behind the voltage.

Advanced Usage

• "To overcome reactance": To design a circuit that minimizes or compensates for the opposition caused by inductance or capacitance.
  • Engineers use specific components to overcome the reactance in the power line.
• "Net reactance": The total reactance in a circuit, which can be the sum of inductive and capacitive reactances (they have opposite signs).
  • At resonance, the net reactance of the circuit becomes zero.

Variants and Related Words

• Capacitive reactance (n): The opposition to current flow caused by a capacitor. It is inversely proportional to frequency.
  • Capacitive reactance is high at low frequencies.
• Inductive reactance (n): The opposition to current flow caused by an inductor. It is directly proportional to frequency.
  • Inductive reactance increases as the AC frequency rises.
• Impedance (n): The total opposition to current flow in an AC circuit, combining resistance and reactance.
  • The speaker's impedance must match the amplifier's output.

Synonyms

• Electrical opposition: A general term for hindrance to current flow.
• AC resistance: An informal term sometimes used to describe reactance, though it is technically imprecise.

Related Phrases

• Reactance theorem: A principle in network analysis relating to energy and reactance.
  • The reactance theorem simplifies the analysis of certain filter networks.
• Skin effect reactance: The component of reactance associated with the skin effect in conductors at high frequencies.
  • At radio frequencies, skin effect reactance becomes significant.

Related Idioms

(Note: As a technical term, "reactance" is not commonly used in idiomatic expressions. However, a conceptual extension exists in psychology.) - Psychological reactance: A motivational state experienced when a person feels their freedom of choice is threatened, leading them to resist. - Telling a teenager they can't do something often triggers psychological reactance, making them want to do it more. (This is a separate, specialized usage from social psychology, not from electrical engineering.)

Học thuật

Noun

1. opposition to the flow of electric current resulting from inductance and capacitance (rather than resistance)