A transformer whose secondary or output voltage is higher that its input or primary voltage is called a step-________ transformer.

• A. Up
• B. Down
• C. Auto
• D. Buck

Answer: (A)

The key idea is how the voltage relates to the number of turns in the windings. If the output (secondary) voltage is higher than the input (primary) voltage, the transformer has more turns on the secondary than on the primary—the turns ratio is greater than one. In that case, the device is called a step-up transformer, because it increases voltage for the next stage of the system (like sending power over long distances where high voltage is advantageous).

In an ideal view, power stays the same (Vp × Ip ≈ Vs × Is), so the higher voltage comes with a proportionally lower current on the secondary side. This is the standard way electricity is transmitted efficiently, then stepped down for end use later on.

The other terms don’t fit this situation as neatly: a step-down transformer would reduce voltage, an auto-transformer can be configured for step-up or step-down but isn’t the conventional name for the separate-winding case here, and buck refers to a DC-DC converter concept rather than an AC transformer winding arrangement.