# Learner lab record: Two-source field map

Course: Matter, energy, fields, and forces

Name: ____________________  Date: ____________________  Group: ____________________

## Investigation question

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.

## Variables

| Variable | Role | Unit |
| --- | --- | --- |
| Source charges q1 and q2 | independent | nC |
| Observation coordinates | independent | m |
| Resultant field vector | dependent | N/C |
| Source positions | controlled | m |

## Predict before changing controls

1. Mark a point where the two contributions may cancel.

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2. Predict how reversing one source changes direction.

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## Observation table

| q1 | q2 | observation point | Ex | Ey | field magnitude |
| --- | --- | --- | --- | --- | --- |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |
|   |   |   |   |   |   |

## Analyze

1. Where did cancellation occur, if anywhere?

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2. Which change affected direction but not source position?

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3. Why is the near-source region bounded?

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4. Draw and label the two component vectors.

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## Evidence-bounded conclusion

At position ___, source 1 contributed ___ and source 2 contributed ___, producing a net field toward ___.

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