Ohm’s Law in Action

Overview

In this tenth lesson of Circuits, Current, and Creativity, students use observations from earlier circuit investigations to develop the relationship (V = I \times R). They calculate a missing voltage, current, or resistance and explain how resistance affects current and component behavior.

Learning intentions

Students will be able to:

• Explain voltage, current, and resistance in a simple circuit.
• Use (V = I \times R) to calculate a missing quantity.
• Describe resistance as opposition to electron flow.
• Connect numerical results to observable component behavior.

Success criteria

• I can identify what voltage, current, and resistance represent.
• I can rearrange and use (V = I \times R) with appropriate units.
• I can explain how increasing resistance changes current when voltage stays the same.
• I can support a claim with a calculation or circuit observation.

Curriculum links

• Washington State mathematics: proportional relationships and interpreting quantities in context, including multiplication and division of rational numbers.
• Washington State mathematics practices: modeling with mathematics and explaining reasoning from real-world contexts.
• Washington State science and engineering learning: using evidence from investigations to explain relationships in electrical systems.
• Literacy in science and technical subjects: interpreting symbols, units, and technical vocabulary in a circuit context.

Lesson structure (40 minutes)

1. 0–5 min · Hook and retrieval. Open with the hook and retrieval slides showing two similar circuits from the class’s earlier observations: one with a brighter lamp and one with a dimmer lamp. Ask, “What might cause the difference if the battery is the same?” Students silently predict, then share one observation and one possible explanation with a partner. Briefly review current, voltage, and resistance.

2. 5–12 min · Build the relationship. Use the voltage-current-resistance teaching slides to introduce voltage as electrical push, current as the rate of charge flow, and resistance as opposition to flow. Model a simple example: if (I=2) amperes and (R=3) ohms, then (V=2\times3=6) volts. Emphasize that the equation describes a relationship, not just a formula to memorize. Students annotate the three quantities, units, and the meaning of resistance on the Ohm’s Law notes and practice sheet.

3. 12–20 min · Worked examples. Model a three-column strategy on the worked-example slides: identify the known values, choose the equation, and solve with units. Complete (I=V\div R) using (V=12) volts and (R=4) ohms, then (R=V\div I) using (V=9) volts and (I=3) amperes. Ask students to estimate whether each answer is reasonable before calculating. Students solve two parallel examples on the worksheet and hold up answers for a quick check.

4. 20–30 min · Partner application. Distribute the Ohm’s Law partner problem set. Partners solve problems involving missing voltage, current, and resistance, including values connected to classroom circuit observations. Require each pair to write one sentence explaining what the answer means; for example, “A larger resistance allows less current when voltage is constant.” Circulate and check that students use units and divide by the correct quantity. Pause halfway for students to compare one solution with another pair.

5. 30–36 min · Evidence discussion. Display the component behavior discussion slides with a comparison: Circuit A has (V=6) volts and (R=2) ohms; Circuit B has (V=6) volts and (R=6) ohms. Students calculate both currents, then discuss: “Which circuit should have greater current, and what component behavior might you expect?” Invite students to use their earlier observations, while clarifying that real components may also heat or behave nonlinearly.

6. 36–40 min · Exit check and preview. Use the exit-ticket and closing slides to display three prompts. Students complete the final item on the worksheet independently: “A circuit has (V=10) volts and (I=2) amperes. Find (R), include the unit, and explain what the resistance means.” They also answer, “If resistance increases while voltage stays constant, what happens to current?” Collect responses and preview the next lesson’s creative circuit design work.

Resources

• the Ohm’s Law instructional slide deck
• the Ohm’s Law notes and practice worksheet
• Projector or interactive display
• Whiteboard and markers
• Calculators, if permitted by classroom routines
• Student circuit observations or previous investigation data
• Pencils and colored pens for annotating quantities and units

Assessment

• During modeling, check students’ use of the equation, rearrangement, units, and reasonableness estimates.
• During partner work, listen for explanations that connect resistance, current, and component behavior rather than reporting only a number.
• Use the exit response to identify whether students can calculate resistance and explain the inverse relationship between resistance and current at constant voltage.

Differentiation

• Provide a formula triangle or equation card, a completed example, and sentence frames such as “When resistance increases, current ___ because ___.”
• Color-code voltage, current, and resistance consistently on the slides and worksheet; read directions aloud and allow students to solve with a partner before independent work.
• For students needing additional support, provide problems with whole-number values and a teacher-led small group during partner practice. Accept verbal explanations or labeled diagrams when writing is a barrier.
• Challenge ready students to create two different circuits with the same voltage but different currents, calculate the required resistances, and explain the predicted component behavior.