Years ago I had an electrician 'very knowledgeably' tell me how it was impossible to receive a shock from a circuit protected by an ELCB (earth leakage circuit breaker)
He expounded to me and a few apprentices that they worked so quick that the electricity would barely run 1 foot up your arm before it tripped. (which is a comical statement in it's own right)
They were a new device in those days and not many knew exactly how they worked.
Trying to sound innocent and interested, I asked him if he would give us a demonstration.
He couldn't resist the temptation and wired one up leaving a bare 240V AC wire poking out.
He flicked it a couple of times like swatting a fly away and nothing happened saying 'there look, I didn't feel a thing'
-'but the ELCB hasn't tripped'
He flicked it again a bit slower....
There was an almighty involuntary scream and the breaker tripped.
One of the apprentices asked 'did you feel anything that time'