Model fields and changes in potential energy

Why does moving interacting objects change stored energy?

Submit: An evidence record, explanation and revision.

Related lesson: Electricity and Magnetism

This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.

Build the idea

For two interacting objects, a field model relates force direction and changes in the energy of the arrangement. Slowly pushing like charges closer requires external work and raises electric potential energy. Letting opposite charges approach can lower potential energy as energy transfers to motion or elsewhere. Potential energy values depend on a chosen reference; changes have physical consequences.

Evidence and model inputs

Conceptual cards: A, two like charges moved slowly closer by an external agent; B, unlike charges released from rest and allowed to approach. Neither card is a safe classroom charge-building instruction. Draw qualitative fields and before/after arrangements; no numerical potential formula is required.

Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.

Materials and preparation

Paper, graph paper or spreadsheet, and the linked readings.

Grade-level scope

Qualitative two-object field and energy models; no potential integrals.

Do the work

1. Draw force arrows on both charges in each card.
2. Mark which external agent does work in A and where its energy goes.
3. For B, model decreasing potential energy and increasing motion or other transfers.
4. Explain how the field model predicts the direction of spontaneous motion.
5. Revise an account that assigns stored interaction energy to a single isolated charge.

Learner worksheet

Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.

Check your reasoning

1. Why does A require external work?
2. What happens to potential energy in B?
3. Do opposite charges have to touch for an interaction?
4. Does a chosen zero make energy changes arbitrary?

Teacher review guide

Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.

1. Draws consistent paired force directions.
2. Connects relative position to potential-energy change.
3. Accounts for external work or released energy.
4. Uses a field model and states the system clearly.

Sources and standard reference

• Official NGSS HS-PS3-5 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.

Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.