Question

this laboratory activity is broken up into four distinct parts so that the goals and variables of each part can be observed separately.
in part i, students manipulate the type of object and document the attraction with a magnet to observe a magnetic field.
in part ii, students manipulate the and document the attraction between the objects to observe an electric field.
in part iii, students intentionally d and measure the electric current generated.
in part iv, students intentionally d and observe the generation of a magnetic field.

Explanation:

In an experiment to observe an electric field, the charge of an object is a key variable. Electric fields are related to the charges on objects. When students manipulate the charge of an object, they can observe the attraction (or repulsion) between objects which is characteristic of electric field interactions. For example, like charges repel and opposite charges attract.

Answer:

charge of an object