Can I use my US hairdryer in Europe?

Only if it is dual-voltage. If it is 110V only, do not use a converter; buy a cheap 230V hairdryer at a local European grocery store or pharmacy for 20 dollars.

Why is my adapter sparking?

If you see sparks, the adapter is loose or the pins aren't making full contact. Unplug it immediately, tighten the fit, or swap the adapter.

How to Safely Power Your Devices in Europe

Most of Europe uses Type C, E, or F plugs with 230V electricity. You need a simple plug adapter for the shape, and a converter only if your device isn't 'dual-voltage' (check the label for 100-240V).

Check your device voltage. Look at the fine print on your charger. If it says 'Input: 100-240V, 50/60Hz', you are safe to use it anywhere in Europe with just a plug adapter. If it says '110V' or '120V' only, you need a heavy-duty power converter to avoid frying your electronics.
Identify the plug type. Most of Europe uses Type C (two thin round pins), which fits into Type E or F sockets. The UK, Ireland, Cyprus, and Malta are the exceptions and require a bulky Type G (three rectangular pins) adapter.
Buy non-grounded vs. grounded adapters. Buy a 'grounded' Type E/F adapter (the one with the side clips or holes) if you are bringing a laptop or high-powered device. If you are just charging a phone, a cheap, slim Type C adapter works perfectly.
Avoid 'universal' bricks. Universal adapters with dozens of sliding parts often get stuck or have loose internal connections. Carry two or three dedicated 'plug-to-plug' adapters instead of one massive, heavy universal block.

Can I use my US hairdryer in Europe?: Only if it is dual-voltage. If it is 110V only, do not use a converter; buy a cheap 230V hairdryer at a local European grocery store or pharmacy for 20 dollars.
Why is my adapter sparking?: If you see sparks, the adapter is loose or the pins aren't making full contact. Unplug it immediately, tighten the fit, or swap the adapter.