Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Does using the em field generated by flowing elctricity cause V drop?

  1. Nov 28, 2013 #1
    I was wondering if you were to use the em field caused by electricity flowing through a wire or coil to push a magnetic or object would you effect the flow of power in the line. Like if you were to wrap a one phase of transmission lines around a solenoid type device to use the em field to push a magnet, would you experience power lose, voltage drop or ?????? in the electrical flow through the line? Also i am licensed electrician but not a college educated electrical engineer, so my terminology may not be 100% on, but I believe this all falls in the realm of inductance. I was basically pondering whether it could be possible to use the power flowing in high voltage transmission lines to power a "charged train" through a tube powered by using the em fields from wrapping these power lines around a "tube" to cause a magnetic push through the tube. Similar to solenoid but on a much grander scale. I get many interesting ideas like this well doing the more mundane aspects of my job and figured it couldn't hurt to ask the pros, but please remember that i am not a engineer so complex formulas may answer the question but help me understand. thanks all happy holidays
    Last edited by a moderator: Dec 3, 2013
  2. jcsd
  3. Nov 29, 2013 #2
    Yes it could be done , but power doesn't come from nowhere , yes the current flow would be affected and given sufficient power consumption voltage would decrease too.

    Basically , If I get ti right what your thinking , it sounds like a linear motor , look up linear electromotors or linear motors, the maglev train works kinda similar , these devices use the changing em field created by current running through coils to push a physical object in one way or the other.
  4. Nov 29, 2013 #3
    yes, after looking into linear motors it seems to be similar to my line of thinking. i was also wondering whether the power consumption to force ratio in linear motors is any better than a traditional electric motor. if you were to say run a chain through the field to create a chain driven system would you get a better ratio from power used to force created. I know there is very little power used when stepping voltage up or down voltage through a transformer and which basically works off inductance through generated em fields. i know you are not creating a force in a transformer and its different ball game but wouldn't you experience less resistance from wind drag and friction in a linear push then in a traditional rotational electric motor. And again thanks crazymechanic. you pointed me in the right direction. if i have time maybe ill post a sketch to help explain my line of thinking.
  5. Nov 29, 2013 #4
    well , if you think about any physical air drag or other factors then I think a properly made both linear and typical electric motor has almoust no loses of that kind , ofcourse if you don't attach a giant propeller to it.

    About the force, every wire , especialy the one which is part of a coil would it be a motor or transformer or an electromagnet experiences force , the force comes from the magnetic field which is created by the current that passes through the wire/coil.
    If you look closely youll see that in both electric motors and transformers the coils are not only laminated but in good devices they are also filled with a sticky and rather strong kind of chemical , paraffin in older models , which is there to prevent coil shaking or ringing or any other physical oscillation that may arise due to magnetic field forces.
  6. Dec 1, 2013 #5


    User Avatar
    Gold Member

    No way to use the field caused by current in a line to do work without "V drop". If you couple to the field, you remove energy from the primary wire when you use it to do work.

    The best physical system is that which provides the best coupling. A linear motor gives you linear motion without gearing and rotational to linear translation. The problem is getting efficient coupling, which is easily achieved in a self contained rotational motor.
  7. Dec 3, 2013 #6


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    It is not valid to try to compare or relate Force and Power in different circumstances. The two are not really related, unless you also consider the movement and speed involved.
    What you probably want is figures for Efficiency of the various types of motor.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook