Which statement is true about a 4:1 transformer, in terms of voltage source side and output?

• A. The secondary produces higher voltage than the primary.
• B. Voltage is the same on both sides.
• C. Voltage depends on frequency.
• D. The primary produces higher voltage than the secondary.

Answer: (D)

In a transformer, the voltages on the primary and secondary sides are set by the turns ratio. A 4:1 transformer means there are four turns on the primary for every one turn on the secondary. That makes the primary voltage four times the secondary voltage: V_p / V_s = N_p / N_s = 4/1, so V_p = 4 V_s and V_s = V_p / 4. Thus the voltage on the source side is higher than the output. The current flips this relation inversely: I_p / I_s = N_s / N_p = 1/4, so the secondary current is higher than the primary current by four, assuming an ideal transformer. The other statements don’t fit because the voltage ratio is determined by turns, not frequency, and a 4:1 step-down yields a lower secondary voltage, not a higher one.