Macbook Pro power supply and grounding.

Hey Apple people. I noticed something disconcerting with the power supply on my MacBook Pro 13" (non-retina)
I have a stainless steel metal table in my kitchen. It is the same type of stainless steel table you find in restaurants.
I have my 13" MacBook Pro in a Speck See-thru case.
The MacBook Pro in it's case is sitting on a Rain Design "M Stand".
The Rain Design "M Stand" is sitting on the stainless steel table.
I am wearing a short sleeve shirt.
I am sitting on a fabric covered chair at the table.
The battery was getting low so I got out my power supply, which is the power brick with the two prong plug adapter.
I plugged this into a power strip and the other end into the computer.
While touching the case of the computer with one hand and leaning on the stainless steel table with my other bare arm. I felt a vibration through the fingers that were in contact with the MacBook Pro. I knew what was going on, and I got really concerned.
I tried an experiment.
I got out the extension cord that came with the MacBook Pro power supply and I changed out the two prong plug on the power supply for the extension cord. The extension cord has a grounding post.
When I plugged the power supply back into the power strip and connected the power supply to the MacBook Pro. I no longer felt a vibrating sensation when I was in contact with the stainless steel table and the computer.
I have other MacBook Pro power supplies and I always use the grounded extension cable with them, because it is located at my regular workstation area. This stainless steel table is located in my kitchen, and I was eating dinner and watching YouTube videos.
Just thought you would like to all know that when you don't use the grounded cable on your MacBook Pro. you become the ground.
Never using this power supply anywhere again without the grounded cable.
Thank you for your time.
Matthew Sievert

It depends on what you are doing.  Yes, the power supply can get hot.  This is normal.

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