Safety boundary
Use simulations, supplied data, and ordinary classroom-static examples only. Do not use mains electricity or improvised high-voltage devices.
Explicit physics instruction
Electric field describes the force per unit positive test charge at a location: E=F/q_test.
Field direction is defined as the direction a positive test charge would accelerate. Around a positive source charge, field points outward; around a negative source, inward.
Field is a property of the source configuration and location, not of the test charge used to measure it.
Vocabulary: electric field; test charge; field direction; source charge; superposition.
Worked example
If a +2 μC test charge experiences 0.010 N east, field magnitude is E=0.010/(2×10⁻⁶)=5000 N/C east.
Guided question
Why does reversing the sign of the test charge reverse its force but not the field itself?
Independent work
- Draw field directions around isolated positive and negative charges.
- Calculate E from three F/q cases.
- Use superposition qualitatively for two-source-charge arrangements.
Misconception check
Electric field and electric force are related but are not the same quantity.
Formative check
What is the operational definition of electric field?
Reveal response
Force per unit positive test charge.
Mentor evidence conference
Ask Archaemenes to audit sign conventions, vector/scalar distinctions, units, and model assumptions.
Teacher guidance
Foundation: Use field-arrow templates.
Core: Calculate E and interpret direction.
Extended: Compare field and force for positive versus negative test charges.