Electrical Quantities - Definitions

Electrical Resistance

  • Resistance

    • Definition: A measure of how much a material or component opposes the flow of electric current.

    • Unit: Measured in Ohms (Ω).

    • Key Concept: The higher the resistance, the more difficult it is for electricity to flow.

Resistivity

  • Resistivity

    • Definition: A property of a material that quantifies how much it resists current flow.

    • Dependent on:

    • Material type

    • Length of the conductor

    • Thickness of the conductor

    • Unit: Measured in micro-ohms per millimetre (µΩ/mm).

Power

  • Power

    • Definition: The rate of doing electrical work or using energy.

    • Importance: Indicates how fast energy is used.

    • Unit: Measured in Watts (W).

    • Formula:

    • P=V×IP = V \times I

      • Where:

      • P = Power

      • V = Voltage

      • I = Current

Frequency

  • Frequency

    • Definition: The number of cycles of alternating current per second.

    • Unit: Measured in Hertz (Hz).

    • Example: In the UK, mains electricity has a frequency of 50 Hz.

Current

  • Current

    • Definition: The flow of electric charge (electrons) through a conductor.

    • Unit: Measured in Amperes (A).

    • Key Concept: One ampere means one coulomb of charge passes a point every second.

Voltage

  • Voltage

    • Definition: Also known as potential difference, it is the electrical pressure that pushes current through a circuit.

    • Unit: Measured in Volts (V).

Energy

  • Energy

    • Definition: The ability to do work.

    • Electrical Terms: The amount of work done when electricity flows.

    • Units: Measured in Joules (J) or kilowatt-hours (kWh).

Impedance

  • Impedance

    • Definition: The total opposition to current in an AC circuit, combining resistance and reactance.

    • Unit: Measured in Ohms (Ω).

Inductance and Inductive Reactance

  • Inductance

    • Definition: The property of a coil that resists changes in current by creating a magnetic field.

    • Unit: Measured in Henrys (H).

  • Inductive Reactance

    • Definition: The opposition to AC caused by inductance.

    • Formula:

    • XL=2πfLX_{L} = 2\pi f L

      • Where:

      • $X_{L}$ = Inductive Reactance

      • $f$ = Frequency (in Hz)

      • $L$ = Inductance (in H)

Capacitance and Capacitive Reactance

  • Capacitance

    • Definition: The ability of a component (capacitor) to store electrical charge.

    • Unit: Measured in Farads (F).

  • Capacitive Reactance

    • Definition: The opposition to AC caused by capacitance.

    • Formula:

    • XC=12πfCX_{C} = \frac{1}{2\pi f C}

      • Where:

      • $X_{C}$ = Capacitive Reactance

      • $f$ = Frequency (in Hz)

      • $C$ = Capacitance (in F)

Power Factor

  • Power Factor

    • Definition: Shows how efficiently electrical power is used in an AC circuit.

    • Measurement: It is the ratio of true power to apparent power.

    • Unit: Dimensionless (value between 0 and 1).

    • Key Concept: A power factor of 1 indicates perfect efficiency.

  • Summary of Electrical Quantities

    • Each quantity plays a vital role in understanding how electrical circuits operate and are interconnected.

    • Understanding these concepts is fundamental for advanced studies in electrical engineering and related fields.