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Question about how current turns on devices .

  1. Mar 27, 2014 #1
    Question about how "current" turns on devices.....

    My apologies up front if this seems like a silly question, but I have not been able to find a straight answer. If "current" is the flow of electrons, and electrons are just charges (negative) - what is that they actually do to turn on a device? They don't release energy/photons etc. Is that other electrons are responding to the electromagnetic force that repulses other electrons - is that how they actually turn something on?

    Thanks in adaance,

  2. jcsd
  3. Mar 27, 2014 #2


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    Heat is generated when current flows through a resistor. A filament light globe produces photons as a result of heat caused by a current.
    When current flows through an inductor it generates a magnetic field that can operate locally or spread through space.
  4. Mar 27, 2014 #3

    jim hardy

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    It's not a silly question. Not everyone is well versed in physics.

    You will probably find this guy's musings about electricity interesting. He's half mad scientist, half philosopher, and half electronics genius.

    He explains things informally but well. His style can hold one's interest long enough for the concepts to sink in.


    Be sure to read his "see also" links, especially the last two. Become aware of concepts and names for charge, current, energy, power, potential. That units are named after people instead of something mnemonic makes them hard to remember.
  5. Mar 28, 2014 #4


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    Simple page: http://www.energyquest.ca.gov/story/chapter01.html
    There are many ways to "turn on" devices.

    One basic circuit would be a battery and a light bulb. The battery has an imbalance of charge and so you can measure a voltage, or electrical pressure between the terminals. It took energy (chemical energy in the case of a battery) to create the charge imbalance, so when the imbalance goes away, the energy must be dissapated somehow. When you connect a wire from the + to the -, the charge flows through the wire to eliminate the imbalance. The flowing charge does 2 things. It creates a magnetic field and (depending on the nature of the wire) it creates heat in the wire. A piece of tungsten wire in the circuit will heat and glow, producing light. A coil around an iron core would create an electro magnet.

    So a device "turns on" because electrons are forced through it by an imbalance of charge that is the source of the electrical energy..
  6. Mar 28, 2014 #5
    Thanks for the responses - I will check out the links. But so far, it does not sound like a "transfer" of energy, more of a "response" to conditions. So bulbs (at least in the incadensent case) "glow" because of heat. Other devices have electrons moving because of magnetism and thus are "turned on"...

    I will tell you what I find.

  7. Mar 28, 2014 #6
    So I think I am gaining a bit of understanding (thanks Jim Hardy for the link). In effect, "electricity" is a bit misleading. I assume, it takes its derivation from the word "electric", more specifically "electric field" - which in itself is misleading. "Electric" sounds very much like "electron", and although electrons have "electric fields," so do protons. Protons have "electric fields," thus "electric" is not necessarily about "electrons."

    These particles have electric fields which act as a force on other particles (yay...I finally '"get" Coulomb's law!!). Thus the "energy" is the force per coulomb, which is proportional to the amount of charge, and indirectly proportional to distance. I.e., the more charge, the more force, the more distance (from the charge) the less force, and therefore less energy. Voltage (which is another topic I need to fully digest) moves the electrons around (the protons are bound in the nucleus and aint going nowhere), the electrons exert forces on other particles causing them to react. With enough reaction, you turn on a device! I presume its like awakening someone who is asleep. A "light" sleeper can be awoken easily (small current), a heavy sleeper needs a slap (lotsa current). Thus when we talk "electricity" it would seem we actually mean the force of the electric field.

    OK, now the question becomes what happens to all the magnetic fields caused by all these moving charges??!! A topic for another time.

    Welcoming thoughts...

  8. Mar 28, 2014 #7

    jim hardy

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    These musings are a good beginning. First we learn vocabulary. Good for you !

    old jim
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