Electrical Engineering › Section B · Resistance, Ohm's law, power, and energy › Topic B.5
Power, efficiency, and energy
Voltage and current tell you how a circuit behaves; power and energy tell you what it costs, how hot it runs and how long a battery lasts. This topic links them, measures how much of the input a machine turns into useful output, and turns kilowatt-hours into dollars.
In this topic
- Power is a rate
- Three forms for a resistor
- Worked example: sizing a resistor
- Who supplies and who absorbs
- Wattmeters
- Efficiency
- Worked example: a pump motor
- Worked example: a chain of stages
- Energy and the electricity bill
- Common mistakes to avoid
- Key takeaways
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