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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.

Parents

  • As Phil Oakley says some chargers give a significant bite from the metal outer of a USB plug due to the capacitor which us connected across the output transformer older supply's were more bighty than newer ones BUT if the socket the charger was plugged into was wired the wrong way round it mite still prove to be a hazard. 

Reply

  • As Phil Oakley says some chargers give a significant bite from the metal outer of a USB plug due to the capacitor which us connected across the output transformer older supply's were more bighty than newer ones BUT if the socket the charger was plugged into was wired the wrong way round it mite still prove to be a hazard. 

Children
  • in reply to Kelly Marie Angel

    if the socket the charger was plugged into was wired the wrong way round it mite still prove to be a hazard. 

    L-N reversal hopefully shouldn't be an issue - since much of the world has unpolarized sockets (pretty much all of Europe), Japan etc. the designs can't presume either of the live pins is "safe". L-PE reversal could be a big issue ... if the USB chargers used the PE connection - none of the ones I've looked at seem to. (which probably makes sense as you wouldn't want earth loops with an interconnected group of USB connected items).

      - Andy.

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