Number of windings for 120-V household circuit?

[a1densmom]

A model train requires 6 V to operate. If the primary coil of its transformer has 240 windings, how many windings should the secondary have if the primary is connected to a 120-V household circuit?


V1/V2 = N1/N2



my teacher went over this with the class, and said that N2= 6V/120V(240), so it equals 12. I don't get how he got that answer. Can someone help me to understand please?

 

[marcusl]

He is correct. This type of transformer is sometimes called a stepdown transformer because it transforms a big voltage to a smaller one. The turns ratio equals the desired voltage ratio, so
n2/240 = 6/120
and n2=12 as claimed.

 

[a1densmom]

I see. Thank you. For some reason, how you wrote it, it clicked in my head.

 

[marcusl]

You're welcome!