What are you plugging into your USB port?
Take it and your MacBook to an Apple store and have it checked out.
Your USB port is 5V, not enough to electrocute you. Something else is wrong.
Im plugging in a 3.5V USB hub
Never heard of such a thing. USB is 5.0V always. Give us a web link to the device.
It is a 5v usb hub but i didn't have a power supply for it so i used a 3.5V and i just try plugging it in without power and it still sparked
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I'm going to test the voltage with a voltmeter (think it is called that) and i will bring it to apple
i tested the same usb hub on my lenovo t430s (without a metal body) and it sparked so it was that usb hub and I'm going to buy http://www.amazon.co.uk/Anker®-Uspe...397574773&sr=8-1&keywords=powered+usb+hub+3.0
The correct 5 volt charger was 5 volts "DC" if you used a generic charger look closely at it as it was probably "AC" which will can cause coniderable damage when used in place of DC.
I live in Arizona, very dry in the summer, and you get static electricity here just from walking on a rug and touching a light switch. You learn to approach a light switch with caution. Anyway I'm using the Plugable 3.0 USB hub on my Mac Pro without incident.
http://www.amazon.com/Plugable-Alum...1397577297&sr=8-3&keywords=plugable+usb+3+hub
Lou
Holy crap man, whatever you are doing, just stop.
Quoted for truth. If it were me I'd return the sparking hub for a refund and try another part.