In a step-down transformer, what happens to voltage and current?

In a step-down transformer, what happens to voltage and current?

• A. Increases the voltage and decreases the current.
• B. Increases the voltage and keeps current constant.
• C. Decreases the voltage and decreases the current.
• D. Decreases the voltage and increases the current.

Answer: (D)

In a step-down transformer, the secondary winding has fewer turns than the primary, so the output voltage is reduced according to the turns ratio: V_secondary = V_primary × (N_secondary / N_primary). Since N_secondary is smaller, V_secondary is lower than V_primary. To keep the power transfer roughly the same (P ≈ P), the current on the secondary side must be higher: I_secondary ≈ I_primary × (N_primary / N_secondary). In other words, voltage drops while current increases, which is why a step-down transformer delivers less voltage but can deliver more current to the load (within efficiency limits).

In a step-down transformer, the secondary winding has fewer turns than the primary, so the output voltage is reduced according to the turns ratio: V_secondary = V_primary × (N_secondary / N_primary). Since N_secondary is smaller, V_secondary is lower than V_primary. To keep the power transfer roughly the same (P ≈ P), the current on the secondary side must be higher: I_secondary ≈ I_primary × (N_primary / N_secondary). In other words, voltage drops while current increases, which is why a step-down transformer delivers less voltage but can deliver more current to the load (within efficiency limits).