An electron of charge a = 1.6 × 10-19C is situated in a uniform electric field of intensity 2.4 × 105 V m-1. What is the force on the electron?

Analyze the question: We are given the charge of an electron, q = 1.6 × 10⁻¹⁹ C, and a uniform electric field of intensity E = 2.4 × 10⁵ V/m. We need the force on the electron.

Concept: The electric field intensity is the force per unit charge:

E = F / q, so F = qE

Solution:

F = (1.6 × 10⁻¹⁹ C) × (2.4 × 10⁵ V/m)

F = (1.6 × 2.4) × 10⁻¹⁹⁺⁵

F = 3.84 × 10⁻¹⁴ N

Checking the options:

• A is just the charge value, so it is wrong.
• B has a positive exponent (10¹⁹), which is far too large.
• C (1.92 × 10⁻¹⁴) is half the correct value, which is a halving error.
• D (3.84 × 10⁻¹⁴ N) matches our result.
• E (7.68 × 10⁻¹⁴) is double the correct value.

Tip: For this type of question, just multiply the coefficients (1.6 × 2.4 = 3.84) and add the powers of ten (−19 + 5 = −14). Always check the exponent sign carefully, since NECO and JAMB often include distractors with a wrong sign or a factor of 2 error.