Does electric heating violates the laws of thermodynamics

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Discussion Overview

The discussion revolves around the efficiency of electric heating devices and whether their operation violates the laws of thermodynamics. Participants explore the implications of energy conversion in electric heaters, the definition of efficiency, and the nature of thermodynamic systems.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions if electric heaters, which convert all input electrical energy to heat, can be considered as having an efficiency of 1 and whether this violates thermodynamic laws.
  • Another participant argues that achieving over-unity efficiency would require producing more heat than the electrical energy supplied, which is not the case for electric heaters.
  • It is noted that an electric heater does not violate thermodynamic laws, as entropy can remain constant in a closed system, and that heaters are typically not closed systems.
  • One participant suggests that electric heaters should not be classified as machines, as they are designed to produce waste heat, contrasting them with heat engines.
  • A claim is made that stating all input energy is converted to heat is an inexact statement and does not accurately reflect efficiency.
  • Another participant clarifies the distinction between thermodynamic efficiency and mechanical efficiency, emphasizing that passive components can affect the latter.

Areas of Agreement / Disagreement

Participants express differing views on the classification of electric heaters and the implications of their efficiency. There is no consensus on whether the statements regarding efficiency and thermodynamic laws are accurate or how they should be interpreted.

Contextual Notes

Participants highlight the complexity of defining efficiency in different contexts, such as thermodynamic versus mechanical efficiency, and the role of passive components in energy systems. Some statements made are noted as potentially inexact or misleading.

mkj
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hello,
we have learned that according to the laws of thermodynamics that the efficiency of any machine should be less than one because of the passive components in it. in an electric heating machine all the input electrical energy is converted to heat. Does this make the electrical heater as an efficiency 1 machine, and does this violates the laws of thermodynamics.
 
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No and no.

To go over-unity it would have to make more heat than the electrical energy supplied to it.

At unity does not violate the laws of thermodynamics: entropy is allowed to stay the same in a closed system.
(It follows that what you were told is not exactly true.)

An electric heater is seldom a closed system.
(Which is, in fact, what you were supposed to get from what you were told.)

https://www.physicsforums.com/showthread.php?t=500095

Technically a heater is a super-inefficient heat engine ... typically 90-99% of the heat goes to the exhaust. It so happens that we want this heat to warm us up.
 
Last edited:
An electric heater is not a machine. It just happens to be a device where you want waste heat. Think of it this way: if you use the heat to heat a boiler and turn a steam engine, then put a brake on it to dissipate the engine's mechanical energy, you'll have the same 100% efficiency of heat production using a 0% efficient steam engine.
 
in an electric heating machine all the input electrical energy is converted to heat.

That's analogous to saying: "all the gasoline used in an engine is converted to heat...and power"...ok, so what...it's an inexact statement and not necessarily a reflection of efficiency.
 
we have learned that according to the laws of thermodynamics that the efficiency of any machine should be less than one because of the passive components in it

Passive components.
mkj - do not mix up efficiency with gain.
A gearbox may have a gain in rpm or torque, but due to frictional losses, its efficiency will be less than 1 ( ie power out < power in ). And that is not a thermodynamic efficiency, but a mechanical efficiency.
 

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