From his experiments, J. J. Thomson concluded that cathode ray particles can move at very fast speeds. cathode ray particles can be moved by electric current. atoms contain small positively charged particles that are called protons. atoms contain small negatively charged particles that are called electrons.

i need mutiple choices

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.