Final answer:
A step-up transformer increases voltage and decreases current, while a step-down transformer decreases voltage and increases current. The number of turns in the coils determines the voltage change.
Step-by-step explanation:
A step-up transformer is designed to increase voltage and decrease current. It has more turns in the secondary coil than in the primary coil. The increase in voltage is achieved by stepping up the voltage in the secondary coil, and this allows for power to be transmitted over long distances with minimum loss. An example of a step-up transformer is the transmission transformer used in electric power distribution.
On the other hand, a step-down transformer is designed to decrease voltage and increase current. It has more turns in the primary coil than in the secondary coil. The decrease in voltage is achieved by stepping down the voltage in the secondary coil. This is useful in applications such as household appliances and electronic devices, where lower voltage is required.