# Electrical4U

> Electrical4U is an educational reference for students, engineers and technicians learning electrical and electronics engineering through explanations, equations and worked examples.

**When to use:** Use Electrical4U when students, engineers or technicians need to understand electricity, voltage, current and resistance; analyse electrical circuits and laws; find electrical engineering formulas and their assumptions; understand transformers, motors and generators; study power generation, transmission, distribution and protection; learn about electronic components and power electronics; understand measurement and control systems; or practise electrical and electronics multiple-choice questions.

**When not to use:** Electrical4U is not an electrical contracting service or a standards authority. It is an educational reference for electrical and electronics engineering.

**How to get started:** Choose a subject in Electrical4U's article directory at https://www.electrical4u.com/electrical-engineering-articles/, then select the relevant lesson. For calculations, find the equation at https://www.electrical4u.com/electrical-engineering-formulas/ and check its units, assumptions and worked examples before applying it. To practise, choose a subject at https://www.electrical4u.com/electrical-engineering-objective-questions-mcq/ and review the answers alongside the lessons.

## Start here

- [Electrical4U home](https://www.electrical4u.com/): Find learning resources, featured articles and the email subscription form.
- [Electrical engineering article directory](https://www.electrical4u.com/electrical-engineering-articles/): Choose a subject and follow its topic page to the individual lessons.
- [Electrical engineering formulas](https://www.electrical4u.com/electrical-engineering-formulas/): Find equations for electrical quantities, power, machines and transformers, with relevant assumptions.

## MCQ practice

- [Electrical engineering multiple-choice questions (MCQs)](https://www.electrical4u.com/electrical-engineering-objective-questions-mcq/): Choose an electrical or electronics subject, practise objective questions and review the answers.

## Topic pages

- [Basic electrical](https://www.electrical4u.com/electrical-engineering-articles/basic-electrical/): Browse lessons on electricity, current, voltage, resistance and electrical power.
- [Circuit theory](https://www.electrical4u.com/electrical-engineering-articles/circuit-theory/): Browse circuit elements, network analysis and circuit-solving methods.
- [Electrical laws](https://www.electrical4u.com/electrical-engineering-articles/electrical-laws/): Find explanations of laws used in circuit analysis and electromagnetism.
- [Engineering materials](https://www.electrical4u.com/electrical-engineering-articles/engineering-material/): Explore the properties and uses of conducting, insulating, magnetic and semiconductor materials.
- [Batteries](https://www.electrical4u.com/electrical-engineering-articles/batteries/): Find lessons on battery types, operation, charging and maintenance.
- [Illumination engineering](https://www.electrical4u.com/electrical-engineering-articles/illumination-engineering/): Study lighting quantities, lamps and illumination principles.
- [Physics](https://www.electrical4u.com/electrical-engineering-articles/physics/): Explore quantum theory, electromagnetism, electrostatics and electron emission.
- [Power generation](https://www.electrical4u.com/electrical-engineering-articles/generation/): Explore power-generation methods and power-station operation.
- [Power transmission](https://www.electrical4u.com/electrical-engineering-articles/transmission/): Find lessons on transmission lines, cables, insulators and transmission-system behaviour.
- [Power distribution](https://www.electrical4u.com/electrical-engineering-articles/distribution/): Learn how distribution networks deliver electrical power to consumers.
- [Switchgear](https://www.electrical4u.com/electrical-engineering-articles/switchgear/): Browse circuit breakers, fuses, isolators and electrical switching equipment.
- [Power-system protection](https://www.electrical4u.com/electrical-engineering-articles/protection/): Study protective relays, fault detection and protection of electrical equipment.
- [Electrical measurement](https://www.electrical4u.com/electrical-engineering-articles/measurement/): Find measuring instruments, meters, bridges, transducers and sensors.
- [Control systems](https://www.electrical4u.com/electrical-engineering-articles/control-system/): Study feedback, system models, stability and control-system analysis.
- [Utilities](https://www.electrical4u.com/electrical-engineering-articles/utilities/): Browse practical references on electrical supplies, equipment and applications.
- [Electrical safety](https://www.electrical4u.com/electrical-engineering-articles/safety/): Learn about electrical hazards, earthing and protective precautions.
- [Transformers](https://www.electrical4u.com/electrical-engineering-articles/transformer/): Browse transformer construction, operation, types, testing and losses.
- [Electric motors](https://www.electrical4u.com/electrical-engineering-articles/electric-motor/): Study motor types, operating principles, starting methods and performance.
- [Generators](https://www.electrical4u.com/electrical-engineering-articles/generator/): Learn how generators and alternators produce electrical power.
- [Electrical drives](https://www.electrical4u.com/electrical-engineering-articles/electrical-drives/): Explore motor-drive selection, control and operating characteristics.
- [Electronic devices](https://www.electrical4u.com/electrical-engineering-articles/electronics-devices/): Browse diodes, transistors and other semiconductor devices.
- [Signal processing](https://www.electrical4u.com/electrical-engineering-articles/signal-processing/): Find lessons on signals, modulation, communications and filtering.
- [Power electronics](https://www.electrical4u.com/electrical-engineering-articles/power-electronics/): Study power semiconductor devices and electrical power-conversion circuits.
- [Digital electronics](https://www.electrical4u.com/electrical-engineering-articles/digital-electronics/): Browse logic gates, digital circuits, codes and number systems.
- [Biomedical instrumentation](https://www.electrical4u.com/electrical-engineering-articles/biomedical-instrumentation/): Explore medical measurement, physiological signals and biomedical instruments.

## Recent posts

- [Electric Current: What is it? (Formula, Units, AC vs DC)](https://www.electrical4u.com/electric-current-and-theory-of-electricity/): Understand charge flow, current units and the differences between alternating and direct current.
- [Voltage: What is it? (Definition, Formula And How To Measure Potential Difference)](https://www.electrical4u.com/voltage-or-electric-potential-difference/): Learn how potential difference is defined, calculated and measured.
- [Programmable Logic Controllers (PLCs): Basics, Types & Applications](https://www.electrical4u.com/programmable-logic-controllers/): Understand industrial controllers, their components, operation and uses.
- [Diode: Definition, Symbol, and Types of Diodes](https://www.electrical4u.com/diode-working-principle-and-types-of-diode/): Learn diode symbols, forward and reverse bias, and common diode types.
- [Thermistor: Definition, Uses & How They Work](https://www.electrical4u.com/thermistor/): Understand temperature-dependent resistance, thermistor types and sensing applications.
- [Half Wave Rectifier Circuit Diagram & Working Principle](https://www.electrical4u.com/half-wave-rectifiers/): Study the circuit, waveforms and calculations for half-wave rectification.
- [Lenz’s Law of Electromagnetic Induction: Definition & Formula](https://www.electrical4u.com/lenz-law-of-electromagnetic-induction/): Determine the direction of induced current and relate it to changes in magnetic flux.

## Popular articles: Circuits and electronics

- [Alphanumeric codes: ASCII, EBCDIC and Unicode](https://www.electrical4u.com/alphanumeric-codes-ascii-code-ebcdic-code-unicode/): Compare ways of representing letters, numbers and symbols in digital systems.
- [Exclusive OR (XOR) gate](https://www.electrical4u.com/exclusive-or-gate/): Understand XOR logic, truth tables and gate implementations.
- [Dry contacts](https://www.electrical4u.com/dry-contacts/): Compare dry and wet contacts and their relay and control applications.
- [Buck-boost converter](https://www.electrical4u.com/buck-boost-converter/): Study the converter circuit, operating principle and output-voltage formula.
- [Solar cell](https://www.electrical4u.com/solar-cell/): Learn how photovoltaic cells convert light into electrical energy.
- [Binary to BCD code converter](https://www.electrical4u.com/binary-to-bcd-code-converter/): Convert binary numbers to binary-coded decimal and examine the conversion logic.
- [MOSFET characteristics](https://www.electrical4u.com/mosfet-characteristics/): Study the operating regions and current-voltage characteristics of metal-oxide-semiconductor field-effect transistors.
- [Nodes, branches and loops of a circuit](https://www.electrical4u.com/nodes-branches-and-loops-of-a-circuit/): Identify the network features used in electrical circuit analysis.
- [Star-delta and delta-star transformations](https://www.electrical4u.com/delta-star-transformation-star-delta-transformation/): Use conversion formulas to simplify three-terminal resistor networks.

## Popular articles: Motors, transformers and transmission

- [Star-delta starter](https://www.electrical4u.com/star-delta-starter/): Study the starter circuit, switching sequence and effect on motor starting current and torque.
- [Direct-on-line (DOL) starter](https://www.electrical4u.com/direct-online-starter-or-dol-starter/): Understand full-voltage motor starting, wiring, overload protection and applications.
- [Overhead electrical insulators](https://www.electrical4u.com/types-of-electrical-insulator-overhead-insulator/): Compare insulator types used to support and insulate overhead power lines.
- [Transformer testing](https://www.electrical4u.com/transformer-testing-type-test-and-routine-test-of-transformer/): Distinguish transformer type tests, routine tests and other diagnostic checks.
- [Open-delta transformer connection](https://www.electrical4u.com/open-delta-connection-of-transformer/): Learn how two transformers supply a three-phase load and the resulting capacity limits.
- [Servo motor](https://www.electrical4u.com/what-is-servo-motor/): Understand servo construction, feedback, operating principles and applications.
- [Transmission lines in power systems](https://www.electrical4u.com/transmission-line-in-power-system/): Study transmission-line types, parameters and equivalent models.

## Popular articles: Measurement, control and protection

- [Tan delta, loss-angle and dissipation-factor tests](https://www.electrical4u.com/tan-delta-test-loss-angle-test-dissipation-factor-test/): Learn how dielectric-loss measurements assess electrical insulation condition.
- [Bode plots, gain margin and phase margin](https://www.electrical4u.com/bode-plot-gain-margin-phase-margin/): Interpret frequency-response plots and assess control-system stability margins.
- [Strain gauge](https://www.electrical4u.com/strain-gauge/): Understand how strain changes resistance and how gauges measure deformation.
- [Restricted earth fault (REF) transformer protection](https://www.electrical4u.com/restricted-earth-fault-protection-of-transformer-ref-protection/): Study the protection arrangement for earth faults within a defined transformer zone.
- [Relay pickup current, plug setting and time setting](https://www.electrical4u.com/pick-up-current-current-setting-plug-setting-multiplier-and-time-setting-multiplier-of-relay/): Understand pickup current, plug-setting multiplier and time-setting multiplier for protective relays.
- [Maximum overcurrent protection (MOCP)](https://www.electrical4u.com/maximum-over-current-protection-mocp/): Interpret equipment overcurrent-protection ratings and distinguish them from minimum circuit ampacity.

## About, contact and policies

- [About Electrical4U and contact details](https://www.electrical4u.com/about/): Learn who the articles serve and how to request coverage of a specific topic.
- [Privacy policy](https://www.electrical4u.com/privacy-policy/): Understand how personal information, cookies, advertising and analytics are handled.
- [Disclaimer](https://www.electrical4u.com/disclaimer/): Read the information-use limitations and advertising and affiliate disclosures.

## Optional

- [XML sitemap](https://www.electrical4u.com/sitemap.xml): Find the wider index of public Electrical4U pages beyond this curated subject and article guide.