I'm having a hard time understanding how the metal band on your countertop could act like a secondary winding driven by the primary in the base of your toothbrush holder/charger. I have such a toothbrush and the magnetic flux in the base is so feeble that moving the tooth brush a fraction of an inch from the base stops the charging effect in the toothbrush. I just can't see any way this weak field could induce a current flow in the counter trim strip. Furthermore, the trim strip is essentially a one-turn secondary. if it's a continuous strip, it's a shorted one-turn secondary with zero volts output, or if not a closed loop, and being one turn only, I believe its induced voltage would be so low as to be imperceptable.
There are other possible causes of the shock that was felt. I would look to see if the whole bathroom lighting and accessory outlets have been wired correctly, and that the ground and hot supply leads weren't mixed up resulting in electrically hot (supposedly) grounded surfaces.
I'm sure there are other cases like this, but I clearly recall a situation in London, England where an electrician mixed the hot and ground leads to a bathroom outlet that resulted in fatally shocking the user of an electric shaver.
Between what two points are you measuring 30 - 50V? You can't get a shock on a closed loop with a circulating current, (see works of Kirchhoff & Lenz), so I assume you measured between the trim and ground. If so, simply patch an incandescent bulb -any wattage- between the same two points and measure again. I wager that the bulb will not light, and the voltage will drop to a few dozen mV, because you have a small capacitive coupling from some energized conductor to the floating trim. Maybe the toothbrush charger or even a hair-dryer power cord. If so, just ground the trim and fuggedaboutit. You can feel currents too small to trip a GFCI, and it's not necessarily dangerous - just startling.
1) I have seen these metal edges on older counters in kitchens or bathrooms to provide a dressed-up trim on either formica or tile counters. This trim was primarily eliminated when granite, CorianTM, and laminated edges were developed and esthetically preferred.
2) I was corrected years ago, by a former Navy Officer, that "Duct" tape is properly called "Duck" tape as it was developed in WW II for the Navy primarily to use in Ships, and Submarines over asbestos pipe insulation. Hence, the reason for the Navy Gray color. It obviously found many other uses including sealing of sheetmetal ductwork.
So was the countertop energized all the time or only when the toothbrush was being charged. Also, was the change generated from the energy going from the base to the toothbrush? How did you rule out the possibility that the base was directly influencing the trim?
I totally agree with 'armorris' on this - the problem could not (well, let me rephrase that a bit - it is highly improbable) be due to the toothbrush charger coupling to the metal rim. There is a leakage path someplace and I would seriously suggest some more aggressive work to figure out what it is. Having something put 30 to 50 V out there is NOT a good thing.
I had a somewhat similar situation a good many years ago. I had added a workbench in a bedroom which was located in the basement (the bedroom and the interior wiring had been added by the previous owner) and, when the workbench's outlets were plugged into the wall outlet, I was getting a 'tingle' when I held a grounded tool. Not good.
I tore into the electrical system downstairs and finally found the culprit - on one of the metal boxes on a homemade extension cord, the screw on the cord clamp was too long and was contacting the hot wire in the cord. This essentially put 120VAC on the ground - the connection was not solid enough for a 'solid' short but did manage to drag the grounds up to about 50 V above earth ground. A very solid 'tingle' indeed.
I'm a retired Electrical Engineer. It is not possible for the coil in the toothbrush charger to induce 30-50 volts into the metal trim on the countertop. That kind of voltage can only come from leakage. If removing the toothbrush charger fixed the problem, then insulation leakage in the charger base is the problem and water has conducted the current to the metal trim. The coupling between the primary coil in the charger (60Hz to maybe 75KHz) is far too small to induce such voltage into the trim on the countertop.
Funny that the charge didn't happen immediately after using the electric toothbrush, or did it? I guess you can count me in with the others who would have opted to replace the counter top because of many reasons, including the charge. But the fix definitely would not have been done with duct tape--white color or otherwise!
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