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

Why electric devices do not draw more current than they need?

  1. Jun 13, 2016 #1
    Tv set is an example You are supplied with 10 amperes Your tv needs 2 ampere Why can not your tv draw current more than 2 amper? If you say because ohm law , this law say that resistance resist current flow This mean the resistor of your tv set will permit flow of only 2 ampers The remaining which is 8 amperes will be prevented by resistor and converted to heat So all the 10 should be consumed by the tv set The tv is an example My question is more general Why the devices does not draw all the available current?
     
  2. jcsd
  3. Jun 13, 2016 #2

    phinds

    User Avatar
    Gold Member
    2016 Award

    You misunderstand completely. You are NOT "supplying" 10 amps, you are supplying some voltage. The TV (or anything hooked up to an electrical power source) draws exactly as much current as it needs and there is no waste anywhere.
     
  4. Jun 13, 2016 #3

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    Why do you think that the 10 amps comes, even if your devices don't use it? It doesn't work that way. The devices in your house draw the power they need from the grid. Power not used by the loads is never generated and never sent on the grid.

    This article might help you understand.
    https://www.physicsforums.com/insights/what-happens-when-you-flip-the-light-switch/
     
  5. Jun 13, 2016 #4

    russ_watters

    User Avatar

    Staff: Mentor

    Amps are a unit of charge flow. Physically, it is a bunch of electrons. Electrons don't get converted to heat.
     
  6. Jun 13, 2016 #5
    Apply a little critical thinking here. if a megawatt nuclear power plant can supply thousands and thousands of amperes at 120V, do you think that a single TV, when connected, will consume it all?
     
  7. Jun 21, 2016 #6

    PhysicoRaj

    User Avatar
    Gold Member

    A water tank contains of gallons of water (charge). The height at which it's placed is the pressure (voltage). The diameter of the outlet pipe(conductance) controls the flow rate (current). Now your resistance being the reciprocal of conductance, analyse how the flow rate (current) varies as you vary the diameter (resistance) as in a tap. You won't get all the water flowing in it at once, only the amount of water that can pass through the given diameter and at given pressure constitutes the flow.
    So holds I=V/R.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Why electric devices do not draw more current than they need?
Loading...