In a transformer, what happens to current when the voltage steps down?

In a transformer, what happens to current when the voltage steps down?

• A. It increases
• B. It decreases
• C. It stays the same
• D. It oscillates

Answer: (A)

When a transformer steps voltage down, the current on the output side increases to keep the power roughly the same. Power in equals power out (P = V × I), so if the output voltage V2 is lower than the input voltage V1, then I2 must be higher than I1 (I2 ≈ I1 × N1/N2). For example, cutting voltage by a factor of five means the secondary current must rise by about five times to deliver the same power, within losses. The primary current will adjust downward accordingly to balance the overall power.

When a transformer steps voltage down, the current on the output side increases to keep the power roughly the same. Power in equals power out (P = V × I), so if the output voltage V2 is lower than the input voltage V1, then I2 must be higher than I1 (I2 ≈ I1 × N1/N2). For example, cutting voltage by a factor of five means the secondary current must rise by about five times to deliver the same power, within losses. The primary current will adjust downward accordingly to balance the overall power.