Electrical Fundamentals
Lesson 5 of 8beginner
14 min read
Electrical Power & Energy
How circuits consume and deliver energy
Theory
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What is Electrical Power?
Electrical power is the rate at which electrical energy is converted into another form of energy (heat, light, motion, sound). It tells you how quickly energy is being used. Power is measured in Watts (W).
Tip
A 60W light bulb converts 60 Joules of electrical energy into light and heat every second.
Power Formulas
There are three equivalent formulas for power, obtained by combining P = IV with Ohm's Law:
- •P = I × V — Power equals current times voltage (the fundamental power equation)
- •P = I²R — Useful when you know current and resistance
- •P = V²/R — Useful when you know voltage and resistance
Energy
Energy is the total amount of work done over time. If power is the rate, energy is the accumulation. Energy (E) = Power (P) × Time (t). The SI unit is the Joule (J), but for household usage we use kilowatt-hours (kWh). 1 kWh = 3,600,000 J.
Key Concept
Your electricity bill measures energy in kWh. A 100W bulb running for 10 hours uses 100 × 10 = 1000 Wh = 1 kWh.
Formulas
Interactive Diagram
Interactive Circuit Diagram
12V
1V24V
100Ω
10Ω1000Ω
Calculator
Enter any 2 values to calculate the rest
Circuit Challenges
Challenge 1 of 3
Calculate Power
A 24V battery drives a current of 0.5A through a circuit. What power is dissipated?
24V
0.5A
? W
Calculate & fill in:
W
Knowledge Check
Question 1 of 5