What is the purpose of a transformer in a mobile phone charger? - Leaving Cert Physics - Question i - 2015

The primary purpose of a transformer in a mobile phone charger is to change the voltage level from the mains supply to a suitable level for charging the mobile phone.

Transformers operate on the principle of electromagnetic induction, which allows them to step up or step down voltage. In the case of a mobile phone charger, a transformer typically reduces the high voltage from the AC mains (e.g., 120V or 240V) to a lower voltage that is appropriate for the battery of the mobile device, such as 5V to 9V.

Additionally, this voltage adjustment is crucial for maintaining safety and enhancing the efficiency of the charging process.