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An electrical experiment for Easter

Chris Pearson

If I have missed something, please let me know.

Introduction

Electrocution has been reported due to the use of a mobile phone in a bath whilst it is plugged into a charger (https://www.rte.ie/news/2025/1001/1536213-inquest-anne-marie-ogorman/). The aim of this study was to establish whether the output of a mobile phone charger can present a risk to the user.

Method

A 5% solution of sodium chloride was placed in stainless steel bowl. The bowl was connected to the earth pin of a twin BS 1363 socket-outlet via an ammeter with a 10 mA full-scale deflection (Avometer Eight Mk 6). A USB charger (Apple Model A1696) was plugged into the adjacent socket-outlet. A USB-C to USB-C cable was plugged into the charger and the other end was immersed in the sodium chloride solution. The charger was energized.

Correct function of the charger was confirmed after the experiment. Confirmation that the earth was effective was obtained by measuring the earth fault loop impedance at the socket outlet.

Results

No current flow was detected. The EFLI was 0.80 ohms.

Discussion

These findings do not confirm the hypothesis that the use of a mobile phone which is connected to a charger whilst taking a bath gives rise to a risk of an electric shock. It may be that the risk exists only if the individual is in contact with the charger itself, or the charger becomes immersed. Further work is required to investigate this alternative hypothesis.

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  • Morning Chris

    I am aware of 3 such type fatal accidents. One in the UK and one in Germany involving IPads being used in the bath.

    I have also read the coroners report from the Anne Marie OGorman fatal accident which in volved an IPhone supplied whilst the victim was using an IPhone supplied from a long USB lead pluged in to a charger inserted in to a hall socket outside the bathroom.

    There is no doubt that the poor woman died from ventricular fibrillation with additional evidence of burns to her body. I understand the plug in charger was not an OEM device. 

    Your experiment was interesting and as a collector of AVO 8s I am aware of the value of the instrument still for some forms of testing. However the input impedance I think is 2000 ohms/volt. If you had used an electronic muti-meter rated for the the voltage, rather than one used for electronics, it will have produced as different reading due to the higher input impedance. 

    Following the German accident I did some experiments on my own Ipad connecting a high input impedance voltmeter on the back I was detecting I remember correctly something in the order of 120V. I then used an oscilloscope to see the peak voltage and it was in the order of 180V with a distorted waveform.

    Being immersed in water substantially increases the risk  of fatal shock hence all of the provisions of BS 7671 701. 

    I believe investigations on the Irish fatal accident are still being worked on. 

    JP

     

  • in reply to John Peckham
    John Peckham said:
    I understand the plug in charger was not an OEM device. 

    John, thank you. It was a toss-up between the AVO and a Fluke digital meter.

    I bought a new iPhone about 13 months ago. Because of the EU's Common Charger Directive, it uses a USB-C port rather than a proprietary one, and it came without a charger.

    That makes very good sense from the point of view of avoiding waste, but it also opens the market to chargers which may be of a lower quality than OEM.

    I wonder what sort of warnings come with a generic charger?

  • in reply to John Peckham

    Sadly John, as you look abroad, there have been quite a few more in the last few years. 

    As I can read German, there is a bit of a bias here to Austria, Germany and Switzerland; but I think we should assume that other places are probably similar at the one or two in hundred million years sort of level.

    https://www.derstandard.at/story/2000146130189/handy-rutschte-in-die-badewanne-junge-italienerin-starb-weil

    https://www.blick.ch/ausland/weil-ihr-ladendes-iphone-ins-wasser-fiel-24-jaehrige-stirbt-in-der-badewanne-durch-stromschlag-id16237529.html

    https://www.sueddeutsche.de/muenchen/handynutzung-stromschlag-in-der-badewanne-16-jaehrige-stirbt-beim-musikhoeren-1.4375817

    https://www.20min.ch/story/handy-faellt-in-die-badewanne-dann-ist-mariantonietta-16-tot-890987304474 

    Interestingly, for females it is now approaching  the no of fatalities from twisted hairdryer flexes failing, the traditional continental mains in the bathroom Bete Noir.

    Due to our regs, in the UK, hairdryers explode mostly in the bedroom but still in similar numbers.  (while the hairdryer in Spain fails mostly over the basin.. ) 

    Given the no of tangled mess leads I have repaired over the years, it is clear that most such failures are non-fatal, and just result in unlady-like language.

    There is no doubt in my mind, that this new trend shows that mobile phones are indeed bad for you.

    Careful with that Ipad.

    Mike.

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