What is the difference between a microphone and a headphone?

Direction that the sound travels is the most basic difference. Any headphone can be used as a microphone and vice versa.

This does also include Piezo elements.

headphones give sound and microphones don't.

Incorrect carlscurry. Try plugging you headphones into a microphone input. It will work just fine as a mic!

It may work both ways, but I wouldn't want to strap microphones onto my head to listen to tunes. And I'd look pretty silly singing karaoke into the headphones, but I'd have to be practically falling down drunk to do it that anyway. It does make for a funny image.

I'd classify the microphone as an input device and headphones as an output device.

The reason that just plugging headphones into a mike socket doesn't work properly is more a question of impedance. (Impedance is the factor that has to be taken into consideration when choosing speakers - plug a 4Ω speaker into a 32Ω output, pump up the volume and fry your output transistors.) Some microphones won't work as loudspeakers - can't be sure but I think the electret might be one, or it might be the ribbon mike. But for the purpose of the questioner, McGruff's answer is right.

I am not basing my answer on speculation. I am basing it on first hand experience.

Technically speaking there is very little difference between the physical and electromagnetic properties of microphones and speakers. Size of element, impedance (resistance in ohms) and design of body are the factors that determine which direction the electromagnetic signals are desired to travel.

I do agree that a speaker should be used as one. Equally true for the microphone.

As for output....It is measured in Watts. This wattage rating is based upon a given or preferred Ohm load. Take a typical 8 Ohm home speaker and hook it up to a 100 Watt car amplifier and it will work beautifully except for the fact that the maximum Wattage output has been cut in half. It is now a 50 Watt amplifier. Conversely...attach a 2 Ohm speaker to the 100 Watt amp and you now have a 200 Watt amp. The distortion level has increased and the heat factor has increased (hence distortion)but the speaker and amp will be just fine indefinately.

The difference then is intended use: Microphones are intended to be spoken into, whereas headphones are intended to be listened to.

The difference is in the current direction. In headphones the electric current goes from the machine to the outside world, in microphones the sound is carried as electricity from the outside world to the machine.

I could not have said it better Arpe!

Thank You!

Headphones sit on your head? lol