Question

a transformer has a primary voltage of 115 v and a secondary voltage of 24 v. if the number of turns in the primary is 345, how many turns are in the secondary? a) 690 b) 72

Explanation:

Step1: Recall transformer voltage - turn ratio formula

The formula for the transformer voltage - turn ratio is $\frac{V_p}{V_s}=\frac{N_p}{N_s}$, where $V_p$ is the primary voltage, $V_s$ is the secondary voltage, $N_p$ is the number of primary turns, and $N_s$ is the number of secondary turns. We need to solve for $N_s$. Rearranging the formula gives $N_s=\frac{V_s\times N_p}{V_p}$.

Step2: Substitute the given values

We are given that $V_p = 115\space V$, $V_s=24\space V$, and $N_p = 345$. Substituting these values into the formula for $N_s$: $N_s=\frac{24\times345}{115}$.
First, calculate $24\times345 = 8280$. Then, divide by 115: $\frac{8280}{115}=72$.

Answer:

B) 72