What does a step up transformer do to current?

A step-up transformer increases the voltage while decreasing the current. According to the principle of conservation of energy, the power in an electrical system remains constant (neglecting losses).

In a transformer, power is equal to the product of voltage and current (P = VI). Therefore, when the voltage increases in a step-up transformer, the current must decrease to maintain the same power output. Conversely, in a step-down transformer, the voltage decreases while the current increases. This relationship is described by the equation for an ideal transformer: V1/V2 = N1/N2 = I2/I1, where V1 and V2 are the voltages on the primary and secondary sides respectively, N1 and N2 are the number of turns on the primary and secondary coils respectively, and I1 and I2 are the currents on the primary and secondary sides respectively.