In a transformer with a turns ratio of 1:4, what happens to current?

In a transformer with a turns ratio of 1:4, what happens to current?

• A. The current remains the same.
• B. The current is stepped up by a 1 to 4 ratio.
• C. The current is stepped down by a 1 to 4 ratio.
• D. The current doubles.

Answer: (C)

When the secondary has four times as many turns as the primary, the transformer raises the voltage by about fourfold. To keep power roughly the same, the current on the secondary must drop to about one-quarter of the primary current. So the current is stepped down by a 1 to 4 ratio. The idea behind this is the inverse relationship between current and turns in an ideal transformer: Vs/Vp = Ns/Np and Is/Ip = Np/Ns. The other options conflict with this inverse relationship or with power conservation.

When the secondary has four times as many turns as the primary, the transformer raises the voltage by about fourfold. To keep power roughly the same, the current on the secondary must drop to about one-quarter of the primary current. So the current is stepped down by a 1 to 4 ratio. The idea behind this is the inverse relationship between current and turns in an ideal transformer: Vs/Vp = Ns/Np and Is/Ip = Np/Ns. The other options conflict with this inverse relationship or with power conservation.