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In The Art of Electronics 3rd, it mentions:

Resistors are used in power circuits to reduce voltages by dissipating power, to measure currents, and to discharge capacitors after power is removed.

I'm not sure what power circuits are, but I found a link (Fundamentals of Electricity: Types of Circuits - Power Circuits) that mentions:

Most lighting and receptacle outlet circuits in a house are power circuits since they only provide power to devices when the devices operate

This suggests that the typical 110 V and 220 V circuits used in homes, as well as the 380 V used in industry, are all power circuits. However, if you were to connect a resistor in series with these 110 V, 220 V, or 380 V circuits to step down the voltage, it would likely burn out the resistor. I’ve never seen this method of voltage reduction before.

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    \$\begingroup\$ You’ve not looked hard enough! The average phone charger, PC power supply and just about any switched power supply does just that. However, it is only done for very low power circuits and frequently only to start the power supply. The bulk of the power conversion is done by other means. \$\endgroup\$ Commented yesterday
  • \$\begingroup\$ @Kartman Thank you for your comment. About "it is only done for very low power circuits", I can understand. Does "power circuits" refer to circuits with 110V, 220V, or 380V? \$\endgroup\$ Commented yesterday
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    \$\begingroup\$ "Power circuit" or power electronics just means anything related to the supply: voltage regulators, tranformers, batteries, suitable cables/connectors etc etc. Not to be confused with the terms "very low voltage", "low voltage" and "high voltage" which are defined voltage ranges. en.wikipedia.org/wiki/Low_voltage \$\endgroup\$ Commented yesterday
  • \$\begingroup\$ @Lundin Thank you for your comment. \$\endgroup\$ Commented yesterday

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No, in this context, power circuits are those where the function of the circuit is to control electrical power or energy rather than carrying out a computational or signal processing operation. So a power supply, voltage regulator or battery charger would be considered a power circuit, but a microcontroller, analogue filter or microphone preamplifier would not. An audio or RF output stage could be argued either way, as I’m sure will follow in the comments.

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  • \$\begingroup\$ A key aspect of this is the care-abouts. In a signal processing situation, one is often caring about many things which can be ignored when analyzing a power-circuit. \$\endgroup\$ Commented 11 hours ago

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