When an iPhone is "dead," it has drained its battery completely and must be recharged and turned back on. Apple's iPhone smartphone device, however, does not have a separate "Power" button. Instead, the device's "Power" button is actually the same as its "Sleep/Wake" button. Without knowing this, powering the device on after it has been dead can be confusing, but after recognizing that the one button has two functions, you can quickly turn on your dead iPhone after a brief charge.
Connect the iPhone's AC charger to a power outlet.
Connect the dock connector end of the AC adapter to the dock connector port on the bottom of the iPhone device. Let the iPhone charge on the AC adapter for at least 15 minutes.
Press and hold the "Sleep/Wake" button on the top of the charging iPhone until the "Apple" logo appears. The dead iPhone will now power on. Leave the iPhone connected to the AC adapter for several minutes to prevent the phone from dying again.