Understand electricity. Calculate with confidence.
A practical electrical engineering library for students, technicians, automotive diagnosticians and EV specialists: clear concepts, verified formulas, working calculators, component guides, safe measurement procedures and interactive simulators.
Browse by domain
Start from the area you are working in, or follow the relationships between concepts, formulas and tools.
Essential concepts
The foundations most searches start with, written at three levels: beginner, intermediate and engineering depth.
What Is Electricity?
Electricity is the presence and motion of electric charge. Learn what charge is, how current flows in a circuit and how electricity carries energy to real loads.
Quantities & UnitsVoltage (Potential Difference)
Voltage is the electrical pressure that drives current. Learn what a volt means, how EMF differs from terminal voltage,...
Electrical LawsOhm’s Law
Ohm’s law links voltage, current and resistance with V = I × R. Learn the formula triangle, the limits of the law and ho...
DC ElectricityDirect Current (DC) Electricity
Direct current flows in one direction at a steady value. Learn DC sources, battery capacity, energy calculations and why...
DC ElectricityVoltage Divider
A voltage divider uses two resistors to produce a fraction of the input voltage. Learn the formula, the loading effect a...
AC ElectricityAlternating Current (AC)
Alternating current reverses direction every half cycle. Learn how AC is generated, how its waveform is described, and w...
Calculators that show the reasoning
Every result includes the formula, the substituted values and the assumptions — never a black box.
Ohm's Law Calculator
Solve V = I × R for voltage, current or resistance and check power.
Electrical Power Calculator
Calculate DC power from voltage, current or resistance using P = VI, P = I²R and P = V²/R.
Electrical Energy Calculator
Convert power and time into watt-hours, kilowatt-hours and energy cost.
Series Resistance Calculator
Total resistance of resistors connected in series, plus current and power for a supply voltage.
Parallel Resistance Calculator
Equivalent resistance of parallel branches and the current in each branch.
Voltage Divider Calculator
Output voltage of a two-resistor divider and the current through it.
Current Divider Calculator
Split a total current between two parallel resistors.
Voltage Drop Calculator
Estimate voltage drop and percentage loss in a cable run.
Structured learning paths
Ordered lessons with objectives, worked examples, key points and end-of-lesson checks.
Electrical Fundamentals
Start from the physical meaning of electric charge and build the core quantities, Ohm’s law, complete circuit...
Electrical Circuit Analysis
Move from a single resistor to real networks. Learn to reduce series and parallel combinations, apply Kirchhof...
Electrical Components
Learn what the common components do, how their value is marked, how they behave in DC and AC circuits, and how...
AC and DC Electricity
Understand the difference between steady direct current and alternating current, read a sine wave correctly, c...
Industrial Electricity
See how industrial power is distributed, how contactors and overload protection control motors, how protective...
Automotive Electrical Systems
Follow the 12 V energy path through a vehicle: battery and alternator, starter circuit, wiring and grounds, an...
Automotive Electronics
Understand how vehicle electronics measure the physical world, process the measurements and command actuators,...
Electric Vehicle Fundamentals
Understand how an electric vehicle stores, converts and delivers energy: the high-voltage architecture, batter...
Interactive simulators
Deterministic, simplified teaching models. They are not installation design or fault-finding tools.
DC Circuit Simulator
Explore a simple DC source and resistive load with live voltage and current.
Series & Parallel Circuit Simulator
Compare series and parallel resistor networks with live current distribution.
Ohm's Law Simulator
Change voltage and resistance and watch current respond.
Voltage Divider Simulator
See how the tap voltage changes with R1 and R2.
Measure, test, diagnose
Safety-first procedures for meters, relays, batteries, charging systems and grounding faults.
How to Use a Multimeter Safely and Correctly
A digital multimeter is the basic instrument of electrical work: it measures voltage, resistance, continuity...
MeasurementsHow to Measure Voltage with a Multimeter
Voltage is a difference in electrical potential between two points, so it can only be measured across someth...
MeasurementsHow to Measure Current with a Multimeter or Clamp Meter
Current is the rate of charge flow, so it is measured through the circuit, not across it. That single fact d...
MeasurementsHow to Measure Resistance with a Multimeter
Resistance is measured with the circuit dead and the component isolated, because the meter supplies its own...
MeasurementsHow to Test Continuity (and What a Beep Really Proves)
A continuity test asks one question: is there a conductive path between these two points? The meter answers...
MeasurementsHow to Measure Voltage Drop Under Load
Voltage drop is the voltage lost across a connection, cable, switch or ground path while current is flowing....
How this library is built
The Electrical Hub separates three things that are often confused: general engineering principles, application-specific values and jurisdiction-specific standards.
Principles before numbers
Definitions and formulas are stated with their conditions of application. We do not invent manufacturer specifications, measurement ranges or standard clauses.
Calculations you can check
The calculation engines are tested against independently computed reference cases. Sizing and automotive tools state their assumptions and are educational, not certified designs.
Safety is part of the content
High-voltage, mains, industrial and EV work requires qualification, isolation and the correct protective equipment. The content never encourages unqualified live work.