Which one of the following common devices works on the basis of the principle of mutual induction ?

The transformer is a common electrical device that operates on the principle of mutual induction [t1][t5]. Mutual induction occurs when a changing electric current in one conducting coil (the primary) induces an electromotive force (EMF) in a second nearby coil (the secondary) through a shared magnetic flux [t5][t8]. This principle allows transformers to 'step up' or 'step down' alternating current (AC) voltages by varying the number of turns in the primary and secondary coils [t5][t7]. In contrast, a tubelight (fluorescent lamp) works on the principle of gas discharge and fluorescence, while Light Emitting Diodes (LEDs) and photodiodes are semiconductor devices [t1][t4]. LEDs operate via electroluminescence in a p-n junction [t4], and photodiodes convert light into current [t9], neither of which relies on mutual induction.

Sources

1. [1] https://pue.karnataka.gov.in/storage/pdf-files/41-I%20PUC%20Electronics%20Textbook.pdf