Unit 08 · Electricity & Magnetism
The year closes with the invisible forces that power the modern world. This unit builds simple circuits — a battery, a wire, a switch, a bulb — and asks what current and voltage actually are, and why a bulb only lights when the loop is complete. From there it links electricity to magnetism: magnets and their fields, and the electromagnet you make by running current through a coil of wire. This is the unit that carries the story of Michael Faraday, the bookbinder’s apprentice who discovered how a moving magnet makes electricity. Mastery means you can build a working circuit and explain the electricity flowing through it.
| Criterion | Developing | Proficient | Mastery |
|---|---|---|---|
| Current & voltage | Cannot say what current or voltage is. | Names them but swaps their meanings. | Describes current as charge flowing and voltage as the push that drives it, in plain terms. |
| Complete circuits | Thinks a bulb lights from a single wire. | Builds a loop but cannot say why it is needed. | Builds a complete loop and explains that current only flows when the circuit is unbroken. |
| “Used-up current” misconception | Believes the bulb uses up the current. | Knows charge flows in a loop but says some is lost in the bulb. | Shows the same current flows all the way around the loop and that the bulb transfers energy, not charge. |
| Magnets & electromagnets | Cannot describe what a magnet does. | Knows magnets attract but confuses a current's field with induction. | Builds an approved electromagnet and distinguishes current producing a field from changing magnetic flux inducing voltage; interprets the assigned induction data and its limits. |
| Lab technique (circuits & electromagnets) | Cannot get a circuit to work. | Lights a bulb but cannot troubleshoot a break. | Builds and fixes simple circuits and an electromagnet, tracing the current through each. |
| Integration (cross-domain) | Makes no supported connection between the source and the science. | Uses the source but needs help connecting evidence, writing, or limitations to the science. | Independently connects History, Reading, and Writing using a cited source, appropriate evidence, a limitation, and a scientific explanation. |
Integration is reported separately and cannot lower the science grade or block a science demonstration pass. Science and practical criteria determine that pass. Use the integration guide's evidence checklist for the separately reported criterion.
Assigned practice: changing flux, voltage, and current
Read the examples and flux definition in OpenStax College Physics 2e, 23.1 and the equation in 23.2, Faraday's and Lenz's law. Distinguish a current creating a magnetic field from a changing magnetic flux inducing an emf. A stationary coil can have an emf when the field through it changes.
Model: average emf = -N times change in flux per turn divided by elapsed time. Flux is in webers, time in seconds, and emf in volts. The chosen loop orientation defines the sign. Emf is not a numerical current measurement: a current estimate also needs a closed-circuit model and electrical properties.
| Case | Turns N | Flux change per turn (Wb) | Time (s) |
|---|---|---|---|
| A | 100 | 0 | 1 |
| B | 100 | 0.0002 | 0.5 |
| C | 100 | -0.0002 | 0.5 |
| D | 100 | 0.0002 | 1 |
Foundation: compare constant flux with changing flux and predict which pair reverses the emf sign. Core: calculate all four average emfs with units. Honors: compare B and D, then state what additional information would be needed to infer current and why an open coil can still have induced emf.
Submit: calculations or the agreed foundation explanation, an annotated orientation sketch, a source-linked explanation in your own words, and one limitation. Transfer: halve N while preserving the flux change and time; the emf magnitude halves. The instructor uses a fresh variation for assessment.
This is the supplied-data evidence for the induction part of the magnets/electromagnets criterion. It does not certify circuit construction or other practical skill. Any physical activity needs a separate instructor-approved low-voltage setup and procedure; no mains, homemade power supply, or unreviewed wiring is authorized.
“The bulb only lit when I closed the switch and completed the loop — break it anywhere and it goes dark. The current isn’t used up in the bulb; the same charge flows all the way around, and the bulb just turns some of that energy into light. Wrap the wire around a nail and the current turns it into a magnet.”
“The bulb uses up the electricity, so there’s less coming back to the battery. A magnet and a battery aren’t really connected, are they?”
Demonstrate the approved circuit/electromagnet skills and complete the assigned induction analysis at the selected level. Distinguish observed practical work from supplied data and explain both current-produced fields and changing-flux emf. A working bulb alone does not meet the induction outcome.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.