The measure of the amount of energy required to move charge between two points which is termed the potential difference. The amount of charge moving per second past a point. It measures the current flow. Lines indicating where the electrical potential is the same. If a voltmeter is used to measure the voltage drop between any two lines then the voltage drop will be the same wherever it is placed on each of the lines 7.
Most electrical current takes the shortest route.
The presence of insulating or conducting features below the ground surface causes deviations in the current flow. They are displaced and this can be detected at the surface by measuring the voltage between two points 9. A reading or group of readings that differ from that expected or the norm. No interpretation is implied by the term. The resistance detected decreases.