Walter Lewin introduced this confusing idea of having loops around a magnetic field. The more loops, the greater the current generated and thus induced emf. Wow, this is how ECE106 theory is used in ECE140.

This is also a video from Engineering Mindset:

Transformers are devices that can either step up or step down AC voltage. They leverage the idea of Electromagnetic Induction to create induced current.

Thanks to transformers, we can plug into AC walls and power both microwaves (2000V) and our smartphones (4V).

where is the number of turns of the coils. Step up transformer Step down transformer