In a perfect world, you'd travel without any electronics, but...
In today's world, you probably have to carry (charge the batteries on) your phone, digital camera, tablet, laptop...
Currents, voltage, and the traveler
American current runs 110V, 60 cycles. Europe runs 210 to 220V and 50 cycles.
Technically, you can't plug an (old fashioned) standard American appliance into a foreign outlet without frying your appliance and/or blowing a fuse. You need a currency converter or transformer to bring the voltage down and the cycles up.
Luckily, nearly all modern devices designed to travel have the converter built in: smartphones, iPads, laptops, digital cameras, hairdryers, etc. Check the bottom panel, the script embossed in the plastic of the charger plug, or the instruction manual to be sure.
Plugs: Flat pegs, meet round holes
Even if your device has a converter built in, you still can't plug an American appliance into a foreign wall because it just plumb won't fit.
American plug prongs are flat and parallel, sometimes with a third, rounded grounding pin. Italy—and most of the rest of Europe—uses two round pins.
(The U.K. uses large, funky plugs made from three huge, flattened fingers of metal arranged in a triangle and set at different angles.)
You can get small plug adaptors that make the switch—I carry several so I can plug in multiple things at once—but these are not currency converters. For older devices, you still need to go through a transformer to get the electrical current running properly.
What electronics to bring
As few as possible, really.
The only pieces of electronic equipment I travel with that isn't battery-powered are my phone, camera, and trusty laptop—and I only need that last one because I have this strange job of writing about my travels.
This hassle is five times worse with anything that has a cord.
Like it says on the Ultimate Packing List, take a small battery-operated alarm clock, and one of those teensy flashlights for poking around ancient ruins and finding stuff in the dark.
Beyond that, try to travel without electronics.
Phone. If you have a smartphone, bring it. It might or might not work abroad (read all about that here), but since it is stuffed with other useful electronic tools (camera, voice recorder, compass, alarm, etc.), it can come in handy on the road. » more
Tablet. If you are a tablet user, bring it along—but remember: anything you lose or break is on you. I actually travel with a small, cheap, Google-branded tablet, primarily because my cellphone is on AT&T, but I can stick in a T-Mobile sim card in the tablet and pay just $20 a month for high-speed data in 150+ countries and then use the tablet for maps, searches, Skype, Yelp, and other handy travel needs. » more
Camera. Since few digital cameras take regular old batteries anymore, only the rechargeable kind, go ahead, pack that charger (and bring a spare battery; you'll use the juice up quickly snapping pics all day). Then again, if your phone has a decent camera on it, you might just stick to that. If makes fewer things to carry around, to worry about losing, and to charge every night.
Hair dryer. A hair dryer, even the teensy portable kind, is just another monkey on your back. Air dry, baby. Or, if you insist on fluffy locks, know that the majority of European hotels from the moderate range up have built-in hair dryers in the bathrooms. If you insist on lugging your own hot air over there, heed my plea and make sure that either it is a travel, dual-voltage hair dryer or that you carry along a converter. Hotels black out on a regular basis when an American plugs in his 110V hairdryer and the appliance either explodes in an impressive shower of sparks or melts in his hands. This stunt has long since ceased to amuse hoteliers and other guests.
Shavers. For shaving, I'd stick with Bic or disposable-head razors unless you have a battery-operated electric shaver—that way you won't have to bother with voltage problems. If not, however, most hotels have a special plug for low-wattage shavers and shavers only. Such outlets are usually identified by an icon of a half-shaven face. If you plug anything other than a shaver in there, you'll join the unpopular hair dryer-melting, fuse-blowing crowd.
Other electronics. If you're planning to bring along any electronic device other than those mentioned above, ask yourself whether you really need it. (Hint : the answer is "no.")
Please turn off all electronic devices as we begin our descent into...
Airlines will request that you don't have your computer, tablet, phone, or any other electronic device turned on during take-off and landing—or at least put the thing into "Airplane" mode (this turns off all antennae and stops it from sending, receiving, or searching for external signals.)
On the off-chance that the waves emitted by these items might foul up the computerized guidance systems, they're hedging their bets against the GPS signal from your iPhone causing the plane to crash.
On the off-chance that they're right, I for one am wholly on their side.