Electric Field Definition Steps:

• The electric field E is produced by the large charge Q at the location of q.
• The force F on q is given by F = qE, from the definition of electric field.
• Newton's third law states the force on Q has the same magnitude F, but this doesn't affect E at q's position.
• Solve for E: E = F / q.

Why D is correct:

• The electric field strength E is defined as the force per unit charge on a test charge, so E = F/q.

Why the others are wrong:

• A: Identical to D, but listed separately—likely a formatting error.
• B: Divides by Q, which is incorrect; E depends on the test charge q, not the source Q.
• C: Multiplies by Q, which has no basis in the field definition.

Final answer: D