Force on a charge in an electric field

Steps:

• The electric force on a charge is given by F = qE, where direction follows the field for positive q and opposes it for negative q.
• The electric field E points vertically upwards.
• The charge q is negative, so qE reverses the direction of E.
• Thus, the force acts vertically downwards.

Why B is correct:

• For a negative charge, F = qE points opposite to E (upwards field yields downward force), as defined by the vector equation F = qE.

Why the others are wrong:

• A: Upwards direction applies to positive charges in an upward field.
• C: No horizontal field component is given.
• D: No horizontal field component is given.

Final answer: B