When a transformer operates with a load, changes in the secondary coil current will cause corresponding changes in the primary coil current. According to the principle of magnetic potential balance, the current of the primary and secondary coils is inversely proportional to the number of turns of the coil. The side with more turns has a smaller current, while the side with fewer turns has a larger current. This can be expressed as follows: primary coil current/secondary coil current=secondary coil turns/primary coil turns.