✔ 最佳答案
The link that is given in your post doesn't work? Thus, I could only give you an answer based on the description from your question.
For an electrical applicance in general, the live wire should not touch the metal case. In case the wire touches the case, the case will become 'lived". That is to say, it carries a potential equal to that of the "live" wire.
But be aware that the existence of a potential doesn't necessary indicate a current is flowing. A current would flow when there is a complete circuit. Although there is a potential on the metal case, there is NO COMPLETE CIRCUIT for any current to flow.
Under this situation, just imagine if your hand happens to touch the metal case, then your hand and body will provide a complete circuit for current to flow from the "live" wire, through the metal casing, your hand and body, then to earth. This causes a current to flow and you would get an electric shock. The fuse would be blown by now.
It is also clear that why there is still current flowing through the heating element when the "live" wire touches the metal case. The reason is simply because the heating element provides a path for a "complete circuit", whereas the metal case doesn't not.
