What is the function of a step-up transformer?

The function of a step-up transformer is to increase voltage. It achieves this by using a primary coil and a secondary coil with differing numbers of turns of wire. When an alternating current passes through the primary coil, it generates a magnetic field that induces a current in the secondary coil. If the secondary coil has more turns than the primary coil, the voltage in the secondary coil will be higher than that in the primary coil, effectively stepping up the voltage. This principle is based on Faraday's law of electromagnetic induction, which states that the induced voltage in a coil is proportional to the rate of change of the magnetic field and the number of turns in the coil.

This ability to increase voltage is crucial in many applications, such as in electrical power transmission, where high voltages are necessary to reduce energy losses over long distances. Therefore, the correct answer identifies the primary role of a step-up transformer in electrical circuits.