Hot iPhone

Click ▷ iPhone too hot? 🔥

Click ▶︎ iPhone User Guide.

There is always a reason a phone gets hot, and that reason is that something on the phone is using a lot of energy. If it gets so hot that it might exceed safe operating limits the phone will shut down and display a message saying it needs to cool off. If it doesn’t do that it isn’t “too hot”. What uses the most energy:

• No cellular network connection: If the phone is not in airplane mode but has not cell towers close enough to connect to it will try to reconnect every couple of minutes, using it’s maximum output power - as cellular radios are only about 30% efficient, 70% of the energy is wasted as heat.
• Weak cellular connection: A 1 bar signal requires 10 times as much energy as a 4 bar signal
• Screen on: The screen uses a lot of energy; the brighter it is set, the more energy
• Camera: The camera will get very hot if left on for long - you can feel it in the case around the camera
• Interactive games with hi rez graphics
• Watching hi rez videos
• Charging with a fast charger (first 80% of charge cycle only)
• An app that is “stuck in a loop” - Shutting down and restarting the phone will usually fix this

In general, anything that uses energy does so at less than 100% efficiency, and the difference between the energy used and the energy supplies becomes heat (this is the 2nd law of thermodynamics)