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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
  • Chris Pearson said:
    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.

    Only for the particular charger you conducted the experiment using and under the particular environmental conditions.

    How do we know an after-market charger wasn't being used?

    I'd perhaps be looking there, although I don't believe all OEM models are the same either - certainly lots of discussion about some designs, for example: discussions.apple.com/.../250613526

Reply
  • Chris Pearson said:
    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.

    Only for the particular charger you conducted the experiment using and under the particular environmental conditions.

    How do we know an after-market charger wasn't being used?

    I'd perhaps be looking there, although I don't believe all OEM models are the same either - certainly lots of discussion about some designs, for example: discussions.apple.com/.../250613526

Children
  • in reply to gkenyon
    gkenyon said:
    Only for the particular charger you conducted the experiment using and under the particular environmental conditions.

    I agree that experiments where N = 1 should be interpreted with caution, but the the report on the Irish case said, "Mr Collins said he had found no fault with either the phone, the charger or the cable ...".

    I imagine that just about every household in the land has at least one mains extension lead. Long USB cables are available, but I cannot help feeling that the mains extension lead became immersed.

    That could be my next experiment.

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