# electricity and electronics

posted by
**annette**
.

a transformer has a primany voltage of 115 v and secondary voltage of 24 v if the number of tures in the primany is 345 how many turns are in the secondary

The voltage ratio

Vsecondary/Vprimary = 24/115 = 0.209

This equals the turns ratio

Nsecondary/Nprimary = Nsecondary/345 = 0.209

Therefore Nsecondary = 72

a man wants to illuminate 5 houses on his model railroad by wiring 5 20 ohm lamps in series.how much resistance must be added in the series in order to limit the current to the .5A needed by each light?

why does tv's, computers, steros, get so dusty