Electrical Quantities - Definitions

These flashcards cover key electrical concepts, definitions, and formulas from the lecture notes on electrical quantities.

What is resistance in electrical terms?

Resistance is how much a material or component opposes the flow of electric current, measured in Ohms (Ω).

What is resistivity and how is it measured?

Resistivity is a property of a material that shows how much it resists current flow, depending on material type, length, and thickness, measured in micro-ohms per millimetre (µΩ/mm).

How is power defined in electricity?

Power is the rate of doing electrical work or using energy, measured in Watts (W). Formula: Power = Voltage × Current (P = V × I).

What does frequency measure in an electrical context?

Frequency is the number of cycles of alternating current per second, measured in Hertz (Hz). In the UK, mains electricity has a frequency of 50 Hz.

What is current and how is it measured?

Current is the flow of electric charge (electrons) through a conductor, measured in Amperes (A). One ampere means one coulomb of charge passes a point every second.

What is voltage?

Voltage (or potential difference) is the electrical pressure that pushes current through a circuit, measured in Volts (V).

How is energy defined in electrical terms?

Energy is the ability to do work, measured in Joules (J) or kilowatt-hours (kWh), and represents the amount of work done when electricity flows.

What is impedance in an AC circuit?

Impedance is the total opposition to current in an AC circuit, combining resistance and reactance, measured in Ohms (Ω).

Define inductance and its measurement.

Inductance is the property of a coil that resists changes in current by creating a magnetic field, measured in Henrys (H).

What is inductive reactance and its formula?

Inductive reactance is the opposition to AC caused by inductance, with the formula Xₗ = 2πfL (Ohms).

What does capacitance refer to in electrical components?

Capacitance is the ability of a component (capacitor) to store electrical charge, measured in Farads (F).

What is capacitive reactance and how is it calculated?

Capacitive reactance is the opposition to AC caused by capacitance, calculated with the formula Xc = 1 / (2πfC) (Ohms).

What does the power factor indicate?

The power factor shows how efficiently electrical power is used in an AC circuit and is the ratio of true power to apparent power, with a value between 0 and 1.