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How do you ground a current in a circuit?

  1. Jun 9, 2014 #1
    So i am relatively new to electronics and i was wondering, on a circuit there will be grounds but its not an actual wire running into the ground, especially on small circuits in phones and stuff, so how is it grounded and what is used to ground it?
     
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  3. Jun 9, 2014 #2
    ground is the name used used when electrons return to their 'ground state' meaning they have no difference of voltage potential between their positive and negative charges. the ground in the dirt is referred to as 'earth ground' and it completes the loop in voltage differences between charges when conducting as a ground. you can think of it as the electrons going from negative to positive always looking to go too an equilibrium state. in a phone with a battery you could think of the negative terminal as being ground, the positive terminal will send electrons through the phone because opposite charges attract each other.

    someone else may want to chime in with why the ground symbol is placed on the negative rail when charges go from negative to positive, I used to know the difference between conventional current flow and the other one??? please enlighten me. lol
     
  4. Jun 9, 2014 #3

    psparky

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    You can't actually "ground it"....in the ground.

    In a residential, commercial or industrial site there are certainly grounds earthed into the earth. The power station has grounds earthed in it's transformers, so all grounds essentially return to their nearest transformer. Hence we must "earth" the grounds so they can get to the "earthed" grounds of it's near transformer supply.

    Your phone or electronics are different because they don't have an AC power plant powering them...

    They instead use a battery. A DC battery.

    Take your car for instance. The entire chasis is grounded to the battery. If you take any 12 volt load and touch its positive terminal to the battery, you can take it's negative terminal and touch it anywhere on the frame. The load will then have current through it. To avoid any short circuits, the car uses a fuse box. If hot touches ground anywhere, this will also short the fuse.

    Your phone and small electronics work the same way. The metal chassis is grounded, little fuse box in there somewhere, hot to negative or hot to ground you get 5 volts DC in many cases. It's grounded, just not into the Earth. You need to ground to your power supply inside of your hand held DC electronic device, not the Earth.

    So in summary, you need to consider where your supply voltage comes from. (yes, your phone plugs into the wall, but what actually powers the phone comes from the small battery inside...not the wall socket. The wall socket does however charge the battery with transformer and full wave recitifier....or other method perhaps)

    Unfortunately, no one has invented a AC battery yet. But even if they did, you will still need to ground to the inside of your electronic hand held device.
     
    Last edited: Jun 9, 2014
  5. Jun 9, 2014 #4

    jim hardy

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    "Ground" is a sloppy term , misused almost universally.

    What it usually means is "Circuit Common" or "Power Supply Return". That may or may not be connected to the earth.

    If you believe Kirchoff's current law, you know that current must get back to where it started. If it leaves the positive end of a flashlight battery it must get back to the negative end of that same battery.

    It is traditional to tie the negative side of a power supply or battery to a point that collects all the currents returning from various loads and call that point "Circuit Common" or "power supply return". A sloppy draftsman or engineer will call it "Ground", even though it has no connection to the earth...

    Car companies still call "Chassis" "Ground" though it's insulated from ground by the tires.
    Missile and aviation stuff that i've seen calls their chassis more correctly, "Vehicle Skin". Obviously an airplane in flight isn't grounded.
    The British use the term "Earth" instead of "Ground" which i like.

    So please form the habit early in your career of calling circuit common by that name, it'll save you confusion later on.

    I use the term "Earth Ground" for a wire sunk into the earth, and i correct people (to their occasional annoyance) who speak of circuit common as "ground". I'm old enough to get away with that but you may not be so proceed judiciously.

    The telephone company does tie their circuit common to earth. So does power company.
    But your TV set's circuit common is very well insulated from earth ground. Else it'd have a three prong power plug.

    If you encounter an old Chrysler or Volkswagen you will find the battery's positive terminal tied to chassis instead of the negative and the car described as "Positive Ground". That's blown up a lot of aftermarket radio installations .

    I know above sounds overly-fastidious but "ground" an important concept. And i'm a potentate-level nerd.

    old jim
     
    Last edited: Jun 9, 2014
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