The amount of induced voltage can be transformed by changing the number of turns of wire in which coil?

• A. Primary
• B. Secondary
• C. Core
• D. Shield

Answer: (B)

The key idea is that the voltage in a transformer winding is proportional to the number of turns in that winding. By Faraday’s law, the induced emf in a winding equals N times the rate of change of the magnetic flux. In a transformer, the magnetic flux in the core is shared, so the output voltage on a winding is set by the turns ratio: Vs ≈ Vp × (Ns/Np). Therefore, changing the number of turns in the secondary winding directly adjusts the transformed voltage—more turns in the secondary produce a higher output voltage. The core mainly provides the magnetic path and coupling, while the shield doesn’t set the voltage.