A transformer has primary turns N_p = 100 and secondary turns N_s = 50. If the primary voltage is 480 V, what is the secondary voltage V_s?

A transformer has primary turns N_p = 100 and secondary turns N_s = 50. If the primary voltage is 480 V, what is the secondary voltage V_s?

• A. 120 V
• B. 180 V
• C. 360 V
• D. 240 V

Answer: (D)

In an ideal transformer, voltages scale with the turns ratio: Vs/Vp = Ns/Np. Here Ns/Np = 50/100 = 0.5, so the secondary voltage is 480 V × 0.5 = 240 V. This means the transformer steps the voltage down by a factor of two. For power balance, the current would roughly double on the secondary (Vp Ip ≈ Vs Is).

In an ideal transformer, voltages scale with the turns ratio: Vs/Vp = Ns/Np. Here Ns/Np = 50/100 = 0.5, so the secondary voltage is 480 V × 0.5 = 240 V. This means the transformer steps the voltage down by a factor of two. For power balance, the current would roughly double on the secondary (Vp Ip ≈ Vs Is).