An iron transformer core is used with removable coils that have different numbers of turns: 200, 400, and 800 turns. One coil is placed on each side of the transformer core. On the primary side, a function generator provides an alternating current (AC) signal at around 4 Hz, and a voltmeter measures the input voltage. On the secondary side, another AC voltmeter measures the output voltage. The ratio of the number of turns on each side of the transformer determines the voltage transformation. According to the principle of electromagnetic induction, the voltage in the secondary coil is proportional to the ratio of the number of turns in the secondary coil to the number of turns in the primary coil. This allows students to observe how altering the number of turns affects the voltage output, illustrating the relationship between coil turns and voltage in transformers based on the turn ratio principle.