Final answer:
A negative charge is usually employed when a partial charge is required in physics.
Step-by-step explanation:
When a partial charge is required, a negative charge which is option C is usually employed. In the context of your question, a partial charge refers to a charge that is less than the full charge of an electron or proton. An example of this is seen in a molecule of water (H2O), where the oxygen atom has a higher electronegativity than the hydrogen atoms, leading to a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms.