# Ground loop- Why would current flow between 2 earth grounds when signal return path offers the least impedance?

Lets say I have 2 ICs- C1 and C2 acting as driver and receiver for the digital signal. The signal is transmitted through a conductor/cable ( 2 wires) as shown below. I have 2 doubts

1. What would be the direction of current flow through GND wire? Will it be alternating? From my limited knowledge in semiconductors, I think when the signal is high, it would charge the internal capacitor of receiver and discharge the same cap when the signal is low. Hence I expect an alternating ( +ve and -ve) current through the cable. Is it correct?

2. Now why would the return current choose the alternate return path? The current would choose the least impedance path, and for an alternating current it is obviously the gnd return path through cable (least inductance path). If any dc component is there it may divide and flow through alternate return path as well.

3. Now what is the problem if at all some dc current flows through alternate return path? There is no EMI issues caused by a dc current.

1. Now lets say a small fraction of ac current flows through earth return path. Is it correct to consider it as a current loop since both the return currents are flowing in the same direction and not really circulating?

So much is written on this which I need to research more . I will proceed after getting clarity on atleast 1st two questions

• Forgot Kirchoffs current law ... ? Oct 23, 2019 at 3:59
• So are you saying, a small fraction of alternating current flows through earth ground return path which causes all the problems? Oct 23, 2019 at 4:19
• @MituRaj Edited the question after rethinking Oct 23, 2019 at 4:27