I know its a fact that Muggle appliances which use electricity don't work in Hogwarts. I can't remember which book this is mentioned in, but I'm sure Hermione says it somewhere. However I thought this was because Hogwarts, and presumably Hogsmeade, had an unusually high concentration of witches and wizards performing magic and therefore in most wizarding homes electrical devices would work. After all, if the Ministry is underneath London, surely the magic used there would affect Muggle devices on the surface?

Basically how much magic does it take before a Muggle device won't work?

I want this for a very specific example- I want a character to listen to her ipod whilst staying at a wizard's house. It's his holiday home, so he's not there 24/7 and, even though she's a Pureblood, her ex-girlfriend is a Half-blood who likes Muggle music and has excellent (i.e my sister's) taste in music, so gave my OC an ipod. I think I can get away with this (the year is 2009) but since my beta queried it I just wanted a second/ third or more opinion.

Thank you- Alex