P=VI watts; in a resistor P=I²R=V²/R.
Power P=VI watts; in resistors also I²R and V²/R. Power is energy per second. Source power equals the sum of power in all loads (conservation). Wires dissipate I²R, so high-voltage transmission reduces losses.
A 60 W lamp at 230 V draws 0.26 A.
Power tells you how much heat and work a component produces, and it sets the power rating needed for resistors and heatsinks.
P=VI watts; in a resistor P=I²R=V²/R.
Power tells you how much heat and work a component produces, and it sets the power rating needed for resistors and heatsinks.
A resistor gets hot when power dissipates in it. Exceeding the rating can damage it or change its value, so choose a rating well above the expected power.
Use P equals I squared R when current is known and P equals V squared over R when voltage is known.
Typical applications include choosing a resistor rated for twice the expected dissipation, estimating the heat from a power supply under load and calculating the energy used by a kettle over a boiling cycle.
Study "Ohm's law" first (topic 5 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
Rated power on appliances. Power ratings of resistors. Peak vs average.
A 60 W lamp at 230 V draws 0.26 A.
The next topic is "Energy and kilowatt-hours", which builds directly on this one.
It is classed as Beginner in Electrical Engineering (topic 6 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.