Ace the Ohio OAE Integrated Science Exam 2025 – Ignite Your Teaching Passion!

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It usually functions by changing the voltage level of alternating current (AC) in power applications.

In the context of the provided options, the laptop charger fits as an example of a transformer because it typically converts the higher voltage AC from the electrical outlet to a lower voltage DC that is suitable for charging the laptop battery. Inside a laptop charger, there are usually coils wrapped around a core that perform the function of a transformer, allowing it to efficiently step down voltage.

Cell phones, while they contain chargers that may also function as transformers, do not explicitly function in the same way as standalone devices. Transistors are semiconductors used for switching and amplification but do not transform voltage. A smart thermostat, though it may control electrical currents, does not have the same function as a transformer because it primarily manages signals rather than converting voltage levels. Thus, the laptop charger is the most appropriate example of a device that acts as a transformer in this context.