Some of us have felt that tingling sensation at one time or another when coming in contact with metallic equipment. But for an electrician, it is a sign that all is not right, especially when the sensation becomes more like a vibration or an intense jolt. The problem arises from electrons wanting to find a return path to the ground. A common culprit is a stray wire inadvertently touching the metal casing via a high-resistance path that is not of sufficient magnitude to trip a breaker.