why does my apple mac book charger get so hot
It may get warm but it should not get hot. Look at this support article:
http://support.apple.com/kb/TS1713
You may consider taking it in to the genius bar for and examination.
Ciao.
When your Macbook's battery is down to say less than 50%, the charger is on a fast charge mode.
Once it gets to around 80% or 90% (can't remember which one), it switches to trickle mode which is less work for your charger and won't be as hot.
If however, your charger is constantly hot when you have a fully charged Macbook, you might have a faulty charger.
If you're under warranty, take it to Apple for a replacement.
If no warranty, have them check it out and replace it with a new one.
why does my charger get hot
