Resistance and Ohm's Law

Active learning works well for resistance and Ohm’s Law because students need to see the invisible—how voltage, current, and resistance interact in real circuits. Hands-on building and measuring help them move past abstract equations into concrete understanding of how components behave in practical setups.

• Year 10
• Physics
• 4 activities
• 20 min–50 min

Learning Objectives

1. Calculate the current, voltage, or resistance in a simple circuit using Ohm's Law.
2. Analyze the graphical relationship between voltage and current for an ohmic conductor.
3. Evaluate how the length, cross-sectional area, and material of a wire affect its resistance.
4. Design an experiment to investigate the factors influencing the resistance of a wire.

Inquiry Circle

⏱ 45 min·Small Groups

Circuit Stations: Ohm's Law Verification

Prepare stations with resistors, power supplies, ammeters, and voltmeters. Students at each station measure current and voltage for three resistors, record data, then plot V-I graphs. Groups swap stations to compare results and identify ohmic behaviour.

Prepare & details

Analyze the relationship between current, voltage, and resistance as described by Ohm's Law.

Facilitation Tip: During Circuit Stations, circulate with a multimeter to troubleshoot connections, reminding students that loose wires cause open circuits and zero current readings.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 30 min·Pairs

Pairs Investigation: Wire Resistance Factors

Provide wires of different lengths, thicknesses, and materials. Pairs connect each to a circuit, measure resistance using a multimeter, and tabulate results. They predict trends before testing and discuss patterns in resistance changes.

Prepare & details

Evaluate how the resistance of a wire changes with its length, cross-sectional area, and material.

Facilitation Tip: For Pairs Investigation, provide labeled wire samples and ensure students record length and diameter before measuring resistance to avoid confusion later.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 50 min·Whole Class

Whole Class: Design Your Experiment

Pose the challenge to verify Ohm's Law. Students brainstorm variables, sketch circuits, and vote on the best design. Implement the class-chosen method, collect shared data, and analyse as a group.

Prepare & details

Design an experiment to verify Ohm's Law for a resistor.

Facilitation Tip: In Design Your Experiment, limit the materials first so groups focus on one variable at a time—thickness, length, or material—before combining factors.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 20 min·Individual

Individual: Calculation Challenges

Distribute worksheets with circuit diagrams and given values. Students calculate missing V, I, or R values, then check by simulating on circuit software. Peer review follows to explain workings.

Prepare & details

Analyze the relationship between current, voltage, and resistance as described by Ohm's Law.

Facilitation Tip: During Calculation Challenges, ask students to verbalize their steps aloud so you can catch unit errors or misplaced decimals early.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Teaching This Topic

Teaching this topic works best when you start with the hands-on activities before introducing the equation V = I × R. Students should discover the relationship themselves through measurement, which makes the math meaningful. Avoid rushing to the formula; let the data guide their understanding. Research shows that students who physically manipulate circuits and plot their own graphs retain the concept longer than those who only watch demonstrations.

What to Expect

By the end of these activities, students should confidently build circuits, measure values, and use V = I × R to solve problems. They should also explain why resistance changes with wire length, thickness, and material through evidence from their own experiments.

Watch Out for These Misconceptions

Common Misconception

During Circuit Stations, watch for students using the mechanical analogy of friction in pipes to explain resistance.

What to Teach Instead

Redirect them to the multimeter readings: ask them to increase resistance in the circuit and observe the drop in current at a fixed voltage, emphasizing the role of electron-atom collisions in the wire.

Common Misconception

During Pairs Investigation, watch for students assuming Ohm’s Law applies to all components like lamps or diodes.

What to Teach Instead

Have them graph voltage versus current for a filament lamp; when the curve bends, ask them to compare it to the straight line they got for a wire, linking the linear relationship to ohmic behavior.

Common Misconception

During Wire Resistance Factors, watch for students predicting that thicker wires have higher resistance.

What to Teach Instead

Ask them to measure two wires of the same material where one is twice as thick, then plot resistance against cross-sectional area to see the inverse trend directly.

Assessment Ideas

Quick Check

After Circuit Stations, set up three mini whiteboards around the room with circuit scenarios (e.g., V = 12V, R = 4Ω; I = 0.5A, R = 20Ω). Ask students to rotate in pairs and solve for the missing variable, holding up their answers for you to check.

Discussion Prompt

During Design Your Experiment, ask each group to present their plan for testing wire length. Listen for explanations that reference more collisions in longer wires and fewer in shorter ones, using their experimental design as evidence.

Exit Ticket

After Calculation Challenges, distribute a one-question exit ticket with a simple V-I graph for an ohmic conductor. Ask students to calculate the resistance, predict the voltage at 3A, and explain why the graph is linear through the origin based on their work with real circuits.

Extensions & Scaffolding

• Challenge students to design a circuit with a 6V battery and two resistors in series, calculating the total resistance and predicting the current before building.
• For students who struggle, provide a partially completed V-I graph with axes labeled and ask them to plot three points using calculated values from V = I × R.
• Deeper exploration: Provide nichrome and copper wires of the same dimensions and ask students to compare their resistances and explain why metals behave differently based on electron density and lattice structure.

Key Vocabulary

Resistance	A measure of how difficult it is for an electric current to flow through a component. It is measured in ohms (Ω).
Ohm's Law	A fundamental law stating that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature remain constant. Mathematically, V = I × R.
Voltage	The electric potential difference between two points in a circuit, measured in volts (V). It is the 'push' that drives current.
Current	The rate of flow of electric charge, measured in amperes (A).
Ohmic Conductor	A component or device that obeys Ohm's Law, meaning its resistance remains constant regardless of the voltage applied or current flowing through it.