![[Unifive] AC adapter & switching power supply manufacturer](common/img/header-logo.svg){kind=logo}
Safe Handling of AC/DC Power Adapters — Desktop & Wall-Mount Part 6: "Do Not Underestimate Low Voltage"
If you underestimate low voltage… This article introduces safe handling of the AC/DC Power Adapters — Desktop & Wall-Mount. The sixth installment features "Don't Underestimate Low Voltage." Generally, even low voltage of 42V can cause serious accidents if used improperly. Please see this article for more details.
Do Not Underestimate Low Voltage
At the end of last year, there was news of a fatal electric shock accident overseas caused by using a smartphone in the bathroom while it was charging. The output voltage of a typical AC adapter is around 5V or 12V, even at most about 48V, so most people would wonder, "Can you really get electrocuted by an AC adapter's output voltage?" However, in the electrical equipment industry, there's a commonly cited phrase: "42V is the killer volt (42V)." This phrase warns that even low voltage, if misused, can be fatal.
The fatal electric shock incident mentioned earlier was not caused by the output voltage of the AC adapter but rather because the input side of the AC adapter was extended into the bathroom using an extension cable. The tragedy occurred when the charging smartphone was accidentally dropped into the bathtub, causing the input voltage to be applied inside the tub. Since the incident happened in a country where the outlet voltage is AC220V—double Japan's voltage—a large current flowed through the person's body, which had a reduced resistance due to being wet. (As you know, current (I) = voltage (V) ÷ resistance (R), according to Ohm's law… so for the same resistance, doubling the voltage results in double the current.) A similar case has also been reported where a person was electrocuted while using headphones plugged into a charging smartphone. (In that case, a leakage issue with the headphones was suspected, but just the thought of current flowing through the head is chilling.)
By the way, since we're talking about electric shocks, do you know why birds don’t get electrocuted when sitting on power lines, but humans do when they touch them? There's a unique and easy-to-understand illustration that explains it clearly at a glance, so please take a look for your reference. (We should aim to explain complex topics as simply as this... m(__)m)
"Even if you touch a power line, it's safe as long as the current doesn't flow through your body. But if it does, you're out."
This time, the point is not only about AC adapters—please make sure not to use products like smartphones in bathrooms or other humid environments while they're charging. To reiterate: "42V is the killer volt." For more information on electric shock, please refer to the links below and take measures to prevent such accidents.
Note 1: This discussion is limited to low voltage situations. With high voltage, even getting close can pose a risk to the human body.
Note 2: According to the technical standards for electrical equipment, "high voltage" means voltages over 750V DC or 600V AC, so "low voltage" refers to those below those values.
"About Electric Shocks" (Hokkaido Electrical Safety Authority)