In an ideal transformer, stepping up the voltage results in what change to current?

In an ideal transformer, stepping up the voltage results in what change to current?

• A. Current increases.
• B. Current decreases.
• C. Current stays the same.
• D. Current becomes zero.

Answer: (B)

Stepping up the voltage in an ideal transformer causes the current on the output side to decrease. Power in equals power out for an ideal transformer, so V1 I1 = V2 I2. When V2 is higher than V1, I2 must be lower than I1 to keep the products equal. The turns ratio ties into this: V2/V1 = N2/N1 and I2/I1 = N1/N2, so increasing voltage implies decreasing current. For example, if voltage doubles, current halves (ignoring losses). The current cannot become zero or stay the same, because energy has to be transferred and the power level remains the same.

Stepping up the voltage in an ideal transformer causes the current on the output side to decrease. Power in equals power out for an ideal transformer, so V1 I1 = V2 I2. When V2 is higher than V1, I2 must be lower than I1 to keep the products equal. The turns ratio ties into this: V2/V1 = N2/N1 and I2/I1 = N1/N2, so increasing voltage implies decreasing current. For example, if voltage doubles, current halves (ignoring losses). The current cannot become zero or stay the same, because energy has to be transferred and the power level remains the same.