In a transformer with Np = 200 turns and Ns = 50 turns, if 120 V is applied to the primary, what is the secondary voltage?

In a transformer with Np = 200 turns and Ns = 50 turns, if 120 V is applied to the primary, what is the secondary voltage?

• A. 60 V
• B. 30 V
• C. 15 V
• D. 120 V

Answer: (B)

In an ideal transformer, the output voltage scales with the turns ratio: Vs = Vp × (Ns/Np). Here, Ns/Np = 50/200 = 1/4. So the secondary voltage is 120 V × 1/4 = 30 V. The primary power is transferred to the secondary, so the secondary current rises by the inverse ratio (Is = Ip × Np/Ns). This is why a transformer with fewer turns on the secondary reduces the voltage proportionally.

In an ideal transformer, the output voltage scales with the turns ratio: Vs = Vp × (Ns/Np). Here, Ns/Np = 50/200 = 1/4. So the secondary voltage is 120 V × 1/4 = 30 V. The primary power is transferred to the secondary, so the secondary current rises by the inverse ratio (Is = Ip × Np/Ns). This is why a transformer with fewer turns on the secondary reduces the voltage proportionally.