In a step-up transformer with a turns ratio of 1:4, which statement is true?

• A. Output voltage is four times the input and output current is four times the input
• B. Output voltage is four times the input and output current is one-quarter of the input
• C. Output voltage equals the input voltage and output current remains the same
• D. Output voltage is one-quarter of the input and output current is four times the input

Answer: (B)

The key idea is how a transformer scales voltage and current with the turns ratio. For a 1:4 step-up transformer, the secondary voltage is four times the primary voltage (Vs = 4 Vp) because the voltage ratio equals the turns ratio. Since power is conserved (ignoring losses), Vp × Ip = Vs × Is. With Vs = 4 Vp, solving for Is gives Is = Ip/4. So the secondary current is one-quarter of the primary current.

That means the statement describing fourfold voltage increase and one-quarter the input current is correct. Choices that say the current would rise instead of fall or that the voltage stays the same don’t match a 1:4 turns ratio, and a statement of voltage stepping down to a quarter would describe the opposite, a step-down.