Question

You generally need a transformer to operate a doorbell because doorbells are designed to work with much smaller voltages than what you typically get from wiring in a house. One particular doorbell needs a potential difference of 16V to work, while the standard outlet voltage (in the United States) is 120V. You have a transformer with 2250 turns in the primary coil. How many turns do you need in the secondary coil to power the doorbell?

Answer 1

Answer: 300 turns

Explanation: In order to explain this problem we have to consider the relationship between the voltage for the primiry and secondary and the turns for their coils.

This expression is consequence of the Faraday law because the magnetic flux is the same for both coils then the induced emf are the same for both circuits.

They are reñated as follow:

Vs=Vp*Ns/Np  where Vs and Vp are the voltage for the secondary and primary coil, respectively.

Ns and Np are the turns for the secondary and primary coil, respectively.

Then we have:

Ns=Vs*Np/Vp= 16*2250/120=300