Power Supply Energy Flow Without Appliance
Country: United States
Date: November 2007
Can electric current run through an extension cord or a
charger cord if it is plugged into a wall but nothing on the other
end? for example, if I leave my cell phone charger plugged in but
the phone is not attached.
Good question. Even though your phone isn't plugged into the charger,
the charger is still there and it will still draw some current. It
will be much less than if it is charging your phone, but it will
still draw some current. Interestingly enough, even if you do not have
anything plugged into any outlet and all your lights and appliances
are turned off, if you measure the current going into your house you
will find that a very small amount of current still flows. This is
called leakage current and happens because the insulation used in
distributing the power is not perfect. To keep things green, you want
to unplug things like chargers if you are not using them.
Hope this helps.
No; electric current cannot flow into a wire that has nothing
at the other end. In your example, though, please note that
the cell phone charger itself will use a small amount of
energy even though no phone is plugged into it. You can feel
that the charger gets slightly warm when left plugged in even
though the phone is not connected to it. This is because the
electrical transformer inside uses a little energy even
though no electrical current is flowing into the cable.
Yes. In the case you give, the charger is running a current
(though it is likely small) because the charger is still converting
the wall voltage to the voltage for your cell phone... even though
the phone is not attached. If it were only an extension cord - just
two wires running to an extension outlet - no current would run.
Those are two different situations.
The answer is: basically no, if nothing at all is plugged into the
extension cord then there is no current. Most chargers draw a small amount
of current, even when the phone is not plugged in, and in this case, yes, a
small current flows. That causes idle or parasitic power to be consumed.
If the power supply feels warm, then it is drawing current and consuming
There are hundreds of millions of chargers in the US, and even if the
current draw is small, it adds up to significant power. You may have
noticed that very modern chargers are cleverly designed to draw negligible
current when plugged in. They do not feel warm at all.
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Update: June 2012