Like most electronic devices, you can power on your Mac with the push a button. If you're unable to power on your Mac, don't panic. Power issues are most commonly the result of a minor oversight -- maybe a loose power adapter or a dead battery -- and there are a number of simple steps that you can take to troubleshoot your problem.
Power on Your Mac
To power on your MacBook, MacBook Air, or MacBook Pro:
Press the power key located on the top-right corner of the keyboard.
To power on your iMac:
With the display facing towards you, press the power button located on the bottom-left corner on the back cover of the display.
To power on your Mac Mini:
With the front facing towards you, press the power button located on the top-right corner on the back of the box
To power on your Mac Pro:
With the rear facing towards you, press the power button located above the power port.
Troubleshoot Your Mac
When you power on your Mac, you will hear a chime and see the Apple logo. If your Mac doesn't power on as it should:
Check to make sure your power adapter is securely connected to your Mac and the electrical outlet. If you're using a Mac Mini or a Mac Pro, make sure your display cable is securely connected.
Connect your Mac's power adapter to a different electrical outlet.
Use a different power adapter.
If your Mac uses a MagSafe adapter, disconnect your adapter from your Mac and the electrical outlet. Wait 60 seconds and then reconnect your adapter.
Press and hold your Mac's power button for 10 seconds, and then press and release the power button.
Follow Apple's guide to reset your Mac's System Management Controller.
If you're still unable to power on your Mac, consult an Apple Store or an Apple Authorized Service Provider for further assistance.