Electric shocks from tip of laptop charger and laptop case - how to safely test if it's a bad charger or a bad outlet?

Solution 1:

No testing needed. Nothing wrong with the outlet can do this in a double insulated device. Replace your charger, ASAP.

This is a safety issue, because it only takes 30 milliamps of 60 Hz current across your chest to stop your heart...

In the United States, the Occupational Safety and Health Administration (OSHA) has published an online brochure that makes the point that grounding won't save you. A grounded (earthed) outlet prong only works if the insulation fault in the equipment is fully connected to a proper ground (cold water pipe or ground stake deep enough in the earth). If you're a better conduction path than the ground conductor, you get the shock instead of the ground wire.

Better than grounding is double insulation -- as long as the device isn't tampered with or damaged, a double insulated device can't shock unless it gets wet or is exposed to conductive dust (metal shavings, etc.). These are recognized by a two-conductor power connection, and often an all-plastic housing.

The only dependable protection (according to OSHA) from insulation fault shocks is a Ground Fault Circuit Interrupter (they go by different names in other countries). These detect tiny differences in the current on the hot and neutral wires (ignoring the ground wire) and shut off the circuit if the two aren't equal. Before you can perceive a shock, the GFCI will shut off the power to the device and trip its warning (usually a visible button popped up, similar to a circuit breaker showing tripped). That's your cue to replace the device, or get it repaired by a professional.