Sorry that your question was not answered sooner - I'm a volunteer and can only take on questions periodically, and there are a lot in my field of science. I image that by now you have had your question answered in another way.
Nevertheless, as an expert in science education, I find it really inappropriate, developmentally, for 3rd graders to be tackling such a task, far too difficult for most. However, it is appropriate for 3rd graders to investigate electricity.
Anyway, an hypothesis is a tentative explanation, a supposition proposed on the basis of limited evidence. It is the starting point for further investigation. Since your child has been studying electricity, the project is likely to be about conductors and insulators. One could hypothesize which, among an array of materials (metal, wood, styrofoam...) which would be better conductors (or insulators).
Electrical conduits are insulated wires (raceways) used to protect cables from damage- they are fire-resistant.
You need to be more specific about the hypothesis, that is the question you want to ask and ultimately test.
The hypothesis is what your child thinks will happen, IF they do a certain action. For example: If I put oil in this water, then it will spread across the surface. Or, If I put detergent in this oily water, then the oil will break down.
Then the child will test the hypothesis to see if it's true. It doesn't have to work. A hypothesis is testing an idea or question. The next step is to modify the hypothesis and then test again.