I know you guys have spent a lot of time proving that electrons don't decay, but could somebody explain what comes out of my one bar electric fire when I switch it on - particularly if its not infrared electromagnetic radiation?
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2$\begingroup$ What is a "one bar electric fire"? And what reason do you have to think it might be exhibiting electron decay? $\endgroup$– David ZCommented Feb 21, 2016 at 12:56
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$\begingroup$ @DavidZ These are electric heaters amazon.co.uk/Team-Nice-Toasty-Traditional-Heater/dp/B0094FZFUC , the resistances are usually in two longitudinal bars and one can just use one bar only, for economy or because it is not too cold. $\endgroup$– anna vCommented Feb 21, 2016 at 14:27
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1$\begingroup$ Of course it is infrared electromagnetic radiation . $\endgroup$– anna vCommented Feb 21, 2016 at 14:28
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$\begingroup$ For Americans "electric fire" is translated as "space heater". $\endgroup$– dmckee --- ex-moderator kittenCommented Feb 21, 2016 at 16:01
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1$\begingroup$ For Eleven, if I might say so, you would be better served by taking some time to learn the foundation of the subject than guessing at what might be going on in the exotic corners. $\endgroup$– dmckee --- ex-moderator kittenCommented Feb 21, 2016 at 16:03
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3 Answers
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Electrons carry energy around, but the do not appear and disappear under ordinary conditions.
Imagine we have a barbecue and a bucket of water we want to heat. We will use a round about method. We takes some rocks and put them on the barbecue until they get hot. Then we put the hot rocks in the water.
When the rocks get hot, they gain energy. They may even get red hot and glow. They lose energy in the water. No rocks are created or lost.
Likewise, no energy has been created or lost. It just changed form and moved around. Chemical energy in the charcoal became heat when the charcoal burned. The heat moved from the fire to the rocks to the water.
answered Feb 21, 2016 at 14:16
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$\begingroup$ Radiation into rocks - radiation out of rocks. Electrons into wires - radiation out, how if not by electron decay ? $\endgroup$– Eleven DCommented Feb 21, 2016 at 15:25
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$\begingroup$ @ElevenD Every electron that goes into a resistor comes out as well. The current is the same on both sides of the resistor. Imagine that you have a fast flowing stream of water that enters a pipe and comes out the other side moving slowly. The flow rate is the same on either side of the pipe, so you don't ask where the water went, you ask were the energy went. $\endgroup$ Commented Feb 21, 2016 at 16:01
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$\begingroup$ It is not entirely radiation in and out of rocks. Heat is transferred by contact too. Here are a couple posts that explain what heat is. physics.stackexchange.com/q/11817/37364 physics.stackexchange.com/a/20023/37364 $\endgroup$ Commented Feb 21, 2016 at 16:07
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$\begingroup$ physics.stackexchange.com/a/114267/108888 I am well aware of thermal conductivity and your posts referring to the speed of sound moved my limited understanding of phonons forward, however, in the end Mr. Einstein said energy essentially comes as radiation and/or mass. Conduction, convection and radiation need supplementing with phase change and at the quantum level the question of whether the mass of an electron decays under any circumstances is important. $\endgroup$– Eleven DCommented Feb 21, 2016 at 22:40
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$\begingroup$ There is no phase change in the wires of an 'electric resistance heater' unless you overload it. Sir Joseph Wilson Swan solved this problem by putting his electric lamp filament in a vacuum where lack of oxygen would prevent degradation of its structure. The vibration of molecules produced incandescence but not burning. Although a visible white light was produced most of the energy emitted was in the infrared. $\endgroup$– Eleven DCommented Feb 21, 2016 at 22:54
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What you have is a resistive heater; the electrical energy goes through a high resistance metal, just like in a toaster, and the wire heats up.
This is conversion of electrical energy to heat; no electrons are lost in this process, but infrared photons are created and radiated towards you by the reflectors.
The efficiency of modern resistance heaters approaches 100%; see http://energy.gov/energysaver/electric-resistance-heating
answered Feb 21, 2016 at 13:00
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$\begingroup$ Where have the electrons gone if the infrared radiation output is not equal to the energy of the electron input ? Heat is not electricity QED. $\endgroup$– Eleven DCommented Feb 21, 2016 at 13:35
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1$\begingroup$ @ElevenD the electrons go around the electrical circuit .hyperphysics.phy-astr.gsu.edu/hbase/electric/ecircon.html . They pick up energy at the power source becoming part of a current, and when they meet the high resistance in the bar they leave most of the energy there as higher kinetic energy in the molecules of the bar, and continue to close the circuit. The bar molecules relax to their lower state giving off infrared radiation that heats the room. $\endgroup$– anna vCommented Feb 21, 2016 at 14:32
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$\begingroup$ Thanks Anna. I understand the number of electrons in the atoms of the wire in these devices remains the same before and after application of any electrical current. And as you explained, to dissipate the energy of increased vibration of the molecules caused by the resistance to the flow of electrons in the wire, radiation has to be given off. These devices are usually rated as a kiloWatt per heater bar. If you put a kiloWatt hour of electricity in - how much radiation do you get out? $\endgroup$– Eleven DCommented Feb 21, 2016 at 16:10
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You may notice that electrical wiring is always done in pairs - current (electrons in motion) flowing one direction in one conductor and the reverse direction in the other conductor. That's because the same quantity of electrons entering a device (lamp, heater, motor, battery, generator) has to leave it. The energy radiated in the heater (or radiated in a light, or work done by a motor) comes from electrons moving from a higher potential (wire at a higher voltage) to a lower potential. The product of potential and rate of flow of electrons equates to the power transferred, and power over a given period of time equates to the total work done. Nowhere in any of this was an electron created or destroyed, simply moved across a potential difference.
In the case of your heater, the energy released as an electron moves through the bar from one conductor to the other (across a difference in potential) ultimately produces photons which carry the infrared or visible light energy from the device.
In summary, the electric fire is an example of the creation of infrared photons due to the movement of electrons, and has nothing to do with electron decay.
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$\begingroup$ I like the idea of electrons flowing in "the reverse direction in the other conductor". Is this mainstream thinking or are you sure they are not positrons ? $\endgroup$– Eleven DCommented Feb 21, 2016 at 22:29
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$\begingroup$ I was trying to explain basic electrical theory. Electrons simply moving around a circuit. They don't get created or destroyed or change in any way, only have energy added (raising potential) or removed (lowering potential). The "reverse" was simply my wording to describe the return path. You are trying to find something exotic in everyday physics where it just doesn't exist. $\endgroup$ Commented Feb 21, 2016 at 23:32