Are you also thinking about use solar flare as a start of the panic and zombie outbreak? :)
About your question. It depends on the strength of the EMP. If the solar flare is strong enough and directed towards earth it would. It might not affect the whole world dependent on how long the flares was active (within 24 hour the world has turned around and then the whole world has been affected).
If you want to know more about this there are some Coast to Coast AM programs that deals with this topic.
Also theres a fiction book by David Crawford that might be inspiring. The name of the book is "Lights Out".
I haven't looked threw this site, but you might find answers here http://www.endtimesreport.com/EMP.html
But of course there are thousands of other places to get info about this. :)
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