I-V Characteristics of Components

Active learning helps students connect abstract voltage-current relationships to the tangible behavior of real components. When students build circuits and plot data themselves, they move from memorising definitions to understanding how resistance changes with conditions like temperature or direction. This hands-on evidence dismantles misconceptions more effectively than passive notes or demonstrations.

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

Learning Objectives

1. Compare the I-V characteristics of ohmic and non-ohmic components by analyzing plotted data.
2. Explain the relationship between temperature and resistance in a filament lamp using its I-V graph.
3. Calculate the resistance of an ohmic component at different voltage points from its I-V characteristic.
4. Classify components as ohmic or non-ohmic based on their I-V characteristic curves.
5. Predict the current flow through a diode at a given forward bias voltage from its I-V graph.

Stations Rotation

⏱ 30 min·Pairs

Circuit Building: Resistor I-V Graph

Pairs connect a resistor, ammeter, and variable power supply in series with a voltmeter across the resistor. They record I and V for voltages from 0-6V in 1V steps, plot the graph, and calculate resistance from gradient. Discuss why the line is straight.

Prepare & details

Differentiate between ohmic and non-ohmic components based on their I-V graphs.

Facilitation Tip: During Graph Matching Relay, rotate groups only after each team has justified at least two graph-component matches to encourage thorough reasoning.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Stations Rotation

⏱ 50 min·Small Groups

Stations Rotation: Component Characteristics

Set up stations for resistor, lamp, and diode. Small groups measure I-V data at each for 10 minutes, swap components, then combine class data to plot shared graphs. Compare shapes and predict resistance changes.

Prepare & details

Explain why the resistance of a filament lamp increases with temperature.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Stations Rotation

⏱ 40 min·Individual

Prediction Challenge: Diode Forward Bias

Individuals sketch expected I-V for a diode from description, then test in circuit with 0.2V steps from 0-1V. Groups share predictions vs results, explaining threshold voltage. Extend to reverse bias.

Prepare & details

Predict the current through a diode given its forward bias voltage.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Stations Rotation

⏱ 20 min·Whole Class

Graph Matching Relay

Whole class divides into teams. Teams match printed I-V graphs to components (resistor, lamp, diode) and justify in relay format: one student runs to board per correct match. Debrief curves.

Prepare & details

Differentiate between ohmic and non-ohmic components based on their I-V graphs.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Teaching This Topic

Teach this topic by letting students experience the mismatch between expectation and reality. Start with resistors to establish the baseline linear relationship, then introduce the lamp and diode to challenge assumptions. Use sequential measurements (e.g., measuring I-V as the lamp heats) to show how conditions alter behavior. Avoid rushing to conclusions; allow time for students to reconcile their observations with their initial ideas.

What to Expect

Success looks like students correctly interpreting I-V graphs and explaining why components behave differently. They should confidently match graphs to components, describe the physical causes behind curvature or flat lines, and use threshold voltage language for diodes. Evidence from their own measurements and discussions should drive their explanations, not just recall.

Watch Out for These Misconceptions

Common Misconception

During Circuit Building: Resistor I-V Graph, watch for students assuming all components will produce straight lines through the origin.

What to Teach Instead

After plotting their resistor data, have students overlay a filament lamp’s I-V graph from Station Rotation. Ask them to compare slopes at different voltages to highlight non-linearity and prompt discussion about temperature effects on resistance.

Common Misconception

During Station Rotation: Component Characteristics, watch for students treating diodes as if they conduct equally in both directions.

What to Teach Instead

During the diode station, ask students to test forward and reverse bias and immediately plot both sets of data on the same axes. Then, have them present their graphs to the class to emphasise the one-way threshold effect.

Common Misconception

During Circuit Building: Resistor I-V Graph, watch for students believing filament lamp resistance decreases when hot because the light is brighter.

What to Teach Instead

Before measuring, ask students to predict how the slope of the I-V graph will change as the lamp heats. After collecting data, pool class results on a whiteboard and discuss how the increasing slope indicates rising resistance.

Assessment Ideas

Quick Check

After Graph Matching Relay, provide students with three unlabeled I-V graphs and ask them to identify each as ohmic, filament lamp, or diode. Require a one-sentence justification for each based on graph shape and component behavior.

Discussion Prompt

During Station Rotation: Component Characteristics, pose the question, 'Why does the filament lamp’s resistance increase as it gets hotter?' Have students reference their data and I-V graphs to explain the relationship between temperature and resistance using particle behavior.

Exit Ticket

After Prediction Challenge: Diode Forward Bias, give students a partial I-V graph for a diode and ask them to extend it to show typical forward and reverse bias behavior. Then, have them predict the current at a voltage 0.5V higher in forward bias, justifying their estimate with the threshold concept.

Extensions & Scaffolding

• Challenge students to design a circuit using a diode that only allows current when a specific voltage threshold is met, and predict its behavior at different temperatures.
• For students who struggle, provide a pre-plotted I-V graph of a diode and ask them to label the forward bias, reverse bias, and threshold voltage before testing.
• Deeper exploration: Have students research how semiconductors in diodes differ from the metal filaments in lamps, linking microscopic structure to macroscopic behavior.

Key Vocabulary

Ohmic component	A component whose resistance remains constant regardless of the voltage applied across it. Its I-V graph is a straight line passing through the origin.
Non-ohmic component	A component whose resistance changes with the applied voltage or current. Its I-V graph is not a straight line.
Resistance	The opposition to the flow of electric current. It is calculated as voltage divided by current (R = V/I).
Filament lamp	A component that produces light when an electric current passes through a thin wire (filament), causing it to heat up and glow.
Diode	A semiconductor device that primarily conducts current in one direction (forward bias) and blocks it in the opposite direction (reverse bias).