There are specific steps that you need to take when developing a hypothesis for your electronics themed science fair projects. The first step is to select a topic related to electronics. Then you will need to ask questions about this topic that you are interested in the answers. For example, you may want to know how the resistance in a wire affects the current and voltage of an electrical charge.
From these questions you will need to focus on a specific hypothesis statement or question to test with your experiments. If you are having a hard time narrowing down your questions to a specific hypothesis to work with then it is a good idea to explore the concepts related to electronics.
An easy way to developing a hypothesis is to work with an electronics lab resource like the MX-908 300-in-1 Electronic Lab.