What is a transformer with more turns on the secondary windings called?

A transformer with more turns on the secondary windings is referred to as a step-up transformer. The fundamental purpose of a step-up transformer is to increase voltage from the primary side to the secondary side. This is accomplished through the principle of electromagnetic induction, where the number of turns in the secondary winding exceeds that in the primary winding.

When the alternating current (AC) flows through the primary coil, it generates a magnetic field that induces a voltage in the secondary coil. The relationship between the number of turns in the windings and the voltages can be described by the turns ratio. If the secondary winding has more turns than the primary winding, the voltage output will be higher than the input, thus "stepping up" the voltage.

This type of transformer is commonly used in applications such as power distribution, where it is necessary to transmit electricity at higher voltages over long distances to reduce energy losses. The other options listed do not fit this description: a step-down transformer decreases voltage, an isolating transformer serves to separate circuits without changing voltage, and a standard transformer is a more general term that does not specifically denote a function related to turns ratio.