Electrical power
Electrical power is the rate at which is transferred, measured in watts (W) or kilowatts (kW). A 1 kW load transfers energy twice as fast as a 500 W load. In a circuit, power equals multiplied by . For AC loads, real power also depends on power factor, so multiplying voltage and current alone does not always give watts.
Free interactive unit · electrical basics
Make the current change
Change one value, watch the circuit respond, then try three short challenges. No sign-up or equipment needed.
Community draft — not yet reviewedWhat this means
This question has not yet been reviewed by a qualified electrician. It is a community draft: check anything you plan to act on against BS 7671 and your own supervisor before you rely on it. Completing it does not make you competent, certified or registered.
Arrows show conventional current direction
- Current
- 1 A
- Resistor power
- 12 W
I = V ÷ R = 12 ÷ 12 ≈ 1 A. Power P = V × I.
1–24 V · use arrow keys for one-volt steps
2–24 Ω · use arrow keys for one-ohm steps
What to notice
Start at 12 V and 12 Ω: current is 1 A. Hold resistance steady and raise voltage. Then reset and raise resistance instead. Watch how the same current reading responds differently.
Your three challenges
0 of 3 explored this visit
Ideal DC source, fixed ohmic resistor and zero wire resistance. This model does not simulate heat, component ratings or real installations. On-screen exploration only; no XP or account progress is saved.
Read the Ohm’s law guide · Explore current · Continue on the learning path
Where Electrical power fits in the learning path
The Electrical Science section covers these units:
- Circuit Fundamentals
Curriculum mapping: C&G 2365 Units 202/302.
See this section in the full curriculum
This section is on the free path. Lesson availability depends on content review and your learning path.
Read, practise, return
1. Read it in context
- Ohm's LawElectrical Science
- Three-Phase PowerElectrical Science
2. Try recalling, then explore practice
Use the memory prompt below to connect the vocabulary.
- Electrical Science — quiz previewFree · Electrical Science
3. Return to the meaning
After reading or practising, explain the idea in your own words. Revisit the Electrical power definition to check what you remembered.
Recall a related term
Which term fits this definition? Say it to yourself, then reveal it. This is a memory prompt, with no score or saved result.
The realistic peak current an installation will draw, worked out from the connected load with diversity applied. It is the figure the supply arrangements are sized against — tails, main switch, distribution equipment — and the first number a designer needs before any circuit-level decisions make sense.
Maximum demand
Read the Maximum demand entryCompare related terms
Open a meaning to compare its role with Electrical power, or follow its full entry.
Maximum demand
The realistic peak current an installation will draw, worked out from the connected load with diversity applied. It is the figure the supply arrangements are sized against — tails, main switch, distribution equipment — and the first number a designer needs before any circuit-level decisions make sense.
Read the Maximum demand entryCurrent
Current is the rate at which electric charge flows, measured in amperes (A), often called amps. In a simple closed circuit, the supply drives current through the load and back to the source. Current is not used up by a lamp: energy is transferred there. A cable current rating describes how much current it can carry in stated conditions, not how much it always carries.
Read the Current entryVoltage
Voltage is the electrical potential difference between two points, measured in volts (V). It describes energy transferred per unit of charge, rather than how much charge is flowing. A battery can have voltage across its terminals even when no complete circuit exists and no current flows. Voltage and current are different quantities.
Read the Voltage entryElectrical energy
Electrical energy is the amount transferred over time, measured in joules (J) or, on electricity bills, kilowatt-hours (kWh). A load drawing a steady 1 kW for two hours uses 2 kWh. Power describes the rate of transfer; energy describes the accumulated amount. A battery capacity quoted in kWh is therefore different from its power rating in kW.
Read the Electrical energy entryA definition is a start. Using it in a real question is where it sticks.