Question

A transformer changes the 10,000 v power line to 120 v. if the primary coil contains 750 turns, how many turns are on the secondary?

Answer 1

For a transformer, the ratio between the number of turns of primary and secondary coil is the same as the ratio between the voltages on the two coils:

`(N_p)/(N_s)= (V_p)/(V_s)`
Where
`N_p` and
`N_s` are the number of turns in the primary and secondary coils, while
`V_p` and
`V_s` are the voltages on the two coils.

Using the data of the problem:
`N_p=750`,
`V_p=10000 V` and
`V_s=120 V`, we can find
`N_s`, the number of turns of the secondary coil:

`N_s=N_p (V_s)/(V_p)=750 (120 V)/(10000 V)=9`