* Input: Cell phones primarily use electrical energy from the battery. This energy was originally stored in the battery by converting chemical energy (from the battery's chemical reactions) into electrical energy when it was charged.

* Output: Cell phones utilize the electrical energy to perform various tasks, ultimately converting it into other forms of energy:

* Lichte energie: The screen emits light energy.

* Sound energy: The speaker produces sound energy.

* Warmte -energie: The phone can get warm due to the conversion of electrical energy into heat.

* Elektromagnetische straling: The phone emits electromagnetic radiation for wireless communication (cell signals, Bluetooth, Wi-Fi).

* Mechanische energie: The vibration motor utilizes electrical energy to produce mechanical energy.

In summary, a cell phone does not produce energy. Instead, it converts electrical energy from its battery into various forms of energy to perform its functions.