A compatible wireless device that is turned off will not receive an emergency alert. If when the device is powered on and the emergency alert is still active and the user is still in the alert area, then the wireless device will display the alert.
A compatible wireless device that is set to silent will display an emergency alert, but you might not hear the emergency alert sound. The emergency alert sound will usually play at whatever the current volume setting is on the wireless device, so if your wireless device is set to silent, no sound will accompany the emergency alert message. However, this behaviour can differ depending on your wireless device and in some instances the alert sound may override your user settings.