What is a common characteristic of a step up transformer?

A step-up transformer is specifically designed to increase the voltage from the primary to the secondary side. This is achieved through the principle of electromagnetic induction, where the number of turns of wire on the primary coil is fewer than that on the secondary coil. As a result, when an alternating current (AC) passes through the primary coil, it generates a magnetic field that induces a higher voltage in the secondary coil due to the additional turns of wire. This transformation of voltage levels is essential in power distribution systems, where higher voltages are required for efficient transmission over long distances.

The other options outline characteristics that apply to different types of transformers. For instance, a transformer that decreases voltage is known as a step-down transformer, while a transformer that maintains the same voltage level is often not referred to as a standard transformer in practical applications. Lastly, while some transformers can provide electrical isolation, this is not a defining characteristic of a step-up transformer, which primarily focuses on voltage increase.