GFI Receptacle : Question

[ElectDesigner]

The way I understand GFI or GFCI receptacle is that there is some sensing circuitry built in that monitors the current between line and neutral and if it different - it cuts off.

My question is this doesnt the appliance being served by the circuit consume energy? and which case wouldnt the difference between line and neutral always be different?

 

[hurk27]

any current supplying a load will return to source on the opposite conductor of that circuit, current is always equal within a complete circuit, this places the currents in each conductor 180? out of phase with each other this cancellation is how the GFCI detects a ground fault, if the currents are not equal then the cancellation is proportional to the amount of imbalance, this starts to produce current in the current coil of the GFCI tripping it when .005 amps is reached.


Down load the attachment and it explains much as to how GFCI's work.

 

[infinity]

In a two wire complete circuit the current is circulating through the load. The current is the same on both conductors of that circuit. If part of that current is somewhere leaking to ground then the current will not be the same on both conductors and the GFCI will sense that and open.

 

[charlie b]

My question is this doesnt the appliance being served by the circuit consume energy? and which case wouldnt the difference between line and neutral always be different?

To add to what the others have said, the GFCI device is not measuring a difference in energy. It is measuring a difference in current.