Level 1 · Foundations teaching kit · Grades 8–9
Matter, energy, fields, and forces
Use the learner record during the live investigation, then use the instructor guide to facilitate comparison, address misconceptions, and assess evidence-bounded reasoning.
Learner lab record
Two-source field map
How do source sign, source strength, and observation position combine into one local field vector?
Setup
Use the field-vector sandbox. Move the observation point and change one source at a time. Keep the minimum-distance boundary visible.
Predict first
- 1. Mark a point where the two contributions may cancel.
- 2. Predict how reversing one source changes direction.
| Variable | Role | Unit |
|---|---|---|
| Source charges q1 and q2 | independent | nC |
| Observation coordinates | independent | m |
| Resultant field vector | dependent | N/C |
| Source positions | controlled | m |
Observation columns
Analyze
- 1. Where did cancellation occur, if anywhere?
- 2. Which change affected direction but not source position?
- 3. Why is the near-source region bounded?
- 4. Draw and label the two component vectors.
Conclusion frame
At position ___, source 1 contributed ___ and source 2 contributed ___, producing a net field toward ___.
Instructor guide · 40–50 minutes
Teach the investigation, not the interface
Learning target: Learners add field contributions as vectors and distinguish a field map from material lines in space.
Prepare
- • Review sign conventions for a positive test charge.
- • Sketch one symmetric two-source arrangement.
- • Plan a no-calculator vector-addition checkpoint.
Facilitation moves
- • Ask for direction before magnitude.
- • Require learners to name the test object convention.
- • Compare a cancellation point with a point merely far from both sources.
Accessibility and participation
- • Pair color with arrow direction and numeric labels.
- • Use tactile arrows or cut paper vectors when useful.
- • Do not require fine pointer placement; keyboard control is equivalent.
Evidence of learning
- • Correct component-vector diagram
- • A controlled sign-reversal comparison
- • Explanation of one model boundary
Misconception checks
Field arrows are physical threads.
They encode the force direction and scale that a test charge would experience locally.
Zero net field means no sources exist.
Nonzero contributions can cancel at a particular location.
Extension
Compare field cancellation with potential addition at the same point.