SCIENCE · INVESTIGATE AND EXPLAIN

Account for charge across an object and its reservoir

Charge accounting begins by choosing recipients and drawing the system boundary. In this packet A, B and a reservoir start neutral. Moving n electrons from A to B leaves A with +ne and gives B −ne. If the reservoir then supplies another m electrons to B, the three final charges are +ne, −(n+m)e and +me. Their total is zero even though the A+B subsystem now has negative charge. Charge has crossed that smaller boundary; it has not been created.

Learning outcome: Hold the first transfer at four electrons and compare reservoir transfers zero, two and six. Retain both subsystem and full-system totals. Draw a separate neutral-polarization picture with no net transferred charge, and explain why an attraction observation would not uniquely identify net sign.

Starting recap

Use signed charge, common coordinate axes, SI units, vector components and algebraic ratios. Separate a source field from probe force and a fitted parameter from independently tested evidence.

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Try

Move four electrons A→B and two reservoir→B. The final ledger in units e is A +4, B −6, reservoir +2. The A+B charge is −2e=−3.204353268×10⁻¹⁹ C; the complete ledger remains zero.

Open the experiment

Predict

After electrons enter B from an external reservoir, which conservation statement is valid?

Your prediction and reason

Experiment

Hold the first transfer at four electrons and compare reservoir transfers zero, two and six. Retain both subsystem and full-system totals. Draw a separate neutral-polarization picture with no net transferred charge, and explain why an attraction observation would not uniquely identify net sign.

Close an electron and reservoir charge ledger

Worked teaching model · synthetic values · Three initially neutral recipients A, B and reservoir R. Only specified electron transfers occur; positive ionic nuclei remain fixed. Elementary charge e=1.602176634e−19 C. No actual charging or grounding activity.

Electrons moved from A to B: 4 electrons Electrons supplied by reservoir to B: 2 electrons

Reset keeps your prediction, captures and practice history.

Include the recipient that exchanges charge

Unlike graph quantities rescale independently; read units and values, not screen angles. 1: signed recipient ledger (open markers). Joined curves show the supplied model, not additional observations.

Equivalent numerical coordinates for Include the recipient that exchanges charge

signed recipient ledger

recipient index (1 A, 2 B, 3 reservoir)	net charge / e
1	4
2	-6
3	2

At most 82 representative computed coordinates including endpoints; the plotted curve can use a finer grid. A table of a revealed generator is not independent measurement evidence.

Calculated quantities under the declared measurement model
Quantity	Value	Unit
A net charge	6.40871e-19	C
B net charge	-9.61306e-19	C
Reservoir net charge	3.20435e-19	C
A plus B net charge	-3.20435e-19	C
Whole closed system net charge	0	C
Transferred electrons counted	6	count

A subsystem can gain charge while the full recipient ledger conserves it.

Removing electrons leaves positive net charge; adding electrons gives negative charge. Electron count is integer here, not a continuous fraction. Neutral polarization separates bound or mobile charge within an object without changing its total. Grounding in a different model exchanges charge with a reservoir; it does not destroy charge or always mean zero object charge.

Predict before inspecting the values. Save contrasting records with assumptions and one alternative explanation. This virtual display does not certify practical measurement technique.

A subsystem can gain charge while the full recipient ledger conserves it.

Observation to attach to a capture

Captures preserve recipes and replay their calculated results. They are synthetic model evidence, not physical measurements.

Understand

Define the source and measurement boundary

Derive the quantitative comparison

The elementary charge magnitude is e=1.602176634×10⁻¹⁹ C. A positive net charge generally means an electron deficit in these fixed-nucleus objects, not that protons traveled along the transfer path. The small numbers in this fictional packet deliberately make quantization visible. A macroscopic coulomb contains an enormous number of elementary charges, so ordinary instrument displays can look continuous without changing the underlying accounting.

Test an alternative before claiming identification

Polarization is different from a net transfer. A neutral insulator can have small bound-charge displacements; a neutral conductor can redistribute mobile electrons. Both can have unequal local charge densities while retaining zero total charge. A polarized neutral object can be attracted in a nonuniform field, so attraction alone does not establish its net charge sign. A grounding connection in a different model exchanges charge with a large reservoir and constrains potential; it does not destroy charge or guarantee that an object near external sources has zero net charge. No physical charging or grounding procedure is requested.

Worked original case

Move four electrons A→B and two reservoir→B. The final ledger in units e is A +4, B −6, reservoir +2. The A+B charge is −2e=−3.204353268×10⁻¹⁹ C; the complete ledger remains zero.

Investigation

Changed-case practice

Try the changed case before feedback

Five electrons move A→B and three more reservoir→B. Report B net charge in units of e, including its sign.

Numerical result in the requested units

This practice is public and unsaved. A matching number does not verify understanding. Retain your explanation, assumptions and changed-case evidence in the separate course workspace.

Sources and evidence boundary

Original teaching, numerical cases and diagrams checked 30 October 2026 against the relevant primary textbook explanation. No textbook exercise, image or passage is reproduced. These are bounded synthetic records, not observed apparatus. No charging, wiring, capacitor handling, medical application or safety certification is requested. Preserve first predictions, contrasting settings and critiques in the course evidence workspace; public feedback is not independent mastery or performed laboratory time.

Apply

Public practice checks a specific claim. It does not establish independent mastery.

Which independent observation could reject this model rather than merely refit its parameters?

Your explanation and limitations

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

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Next: Test an inverse-square force after removing a baseline

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