In a step-up transformer, doubling the output voltage results in approximately halving the output current, assuming constant VA.

In a step-up transformer, doubling the output voltage results in approximately halving the output current, assuming constant VA.

• A. Decreases
• B. Increases
• C. Remains the same
• D. Unpredictable

Answer: (A)

When a transformer steps voltage up, power has to balance. In an ideal transformer, the apparent power on the primary roughly equals the apparent power on the secondary: Vp × Ip ≈ Vs × Is. If you doubles the output voltage (Vs) while keeping the same VA, the secondary current (Is) must drop proportionally to keep the product Vs × Is constant. So doubling voltage results in about half the current. For example, if the secondary delivers 600 VA, increasing voltage from 120 V to 240 V requires reducing current from 5 A to 2.5 A. The other options would violate the constant VA condition or imply unpredictability, which isn’t the case here. Therefore, the output current decreases.

When a transformer steps voltage up, power has to balance. In an ideal transformer, the apparent power on the primary roughly equals the apparent power on the secondary: Vp × Ip ≈ Vs × Is. If you doubles the output voltage (Vs) while keeping the same VA, the secondary current (Is) must drop proportionally to keep the product Vs × Is constant. So doubling voltage results in about half the current. For example, if the secondary delivers 600 VA, increasing voltage from 120 V to 240 V requires reducing current from 5 A to 2.5 A. The other options would violate the constant VA condition or imply unpredictability, which isn’t the case here. Therefore, the output current decreases.