Current, Potential Difference, and Resistance

Active learning works for this topic because circuits demand visual, tactile, and quantitative evidence to replace prior misconceptions about invisible charge movement and energy transfer. When students build, measure, and graph in real time, Ohm’s Law shifts from abstract notation to concrete experience.

• Year 12
• Physics
• 4 activities
• 20 min–50 min

Learning Objectives

1. Calculate the current, potential difference, or resistance in a simple DC circuit using Ohm's Law.
2. Compare the current-voltage (I-V) characteristics of ohmic and non-ohmic components.
3. Design a circuit to investigate how changing resistance affects current and potential difference.
4. Explain the relationship between power, current, and potential difference in a circuit.
5. Analyze how changes in voltage affect power loss in a transmission line.

Stations Rotation

⏱ 45 min·Small Groups

Stations Rotation: Ohm's Law Circuits

Set up stations with batteries, resistors, ammeters, and voltmeters. Students connect in series, vary voltage, record current and potential difference, then plot V-I graphs. Switch resistors to compare resistances. Calculate R from gradients.

Prepare & details

Explain how the drift velocity of electrons compares to the speed of the electric signal in a wire.

Facilitation Tip: During Station Rotation: Ohm's Law Circuits, set up each station with a different resistor value and require students to complete a table of calculations before moving to the next station to prevent rushing.

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

Problem-Based Learning

⏱ 35 min·Pairs

Pairs Investigation: Ohmic vs Non-Ohmic

Pairs build parallel circuits: one with a fixed resistor, one with a filament lamp. Use a variable supply to measure I-V data points. Plot graphs and discuss why one is linear and the other curves upward.

Prepare & details

Analyze the variables that affect the efficiency of power delivery across a national grid system.

Facilitation Tip: During Pairs Investigation: Ohmic vs Non-Ohmic, ask pairs to sketch their predicted I-V graphs before collecting data, then compare predictions to results to build metacognitive awareness.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Problem-Based Learning

⏱ 20 min·Whole Class

Whole Class Demo: Signal vs Drift Speed

Connect a long wire (5m+) with bulbs at both ends to a battery switch. Time light-up to show fast signal. Contrast with slow drift via electron model animation discussion. Students predict and verify.

Prepare & details

Design a simple circuit to demonstrate the relationship between current, voltage, and resistance.

Facilitation Tip: During Whole Class Demo: Signal vs Drift Speed, use a long transparent tube with small beads to model charge movement, then measure time delays to make abstract speeds tangible.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Problem-Based Learning

⏱ 50 min·Small Groups

Design Challenge: Series-Parallel Efficiency

Provide components; groups design circuits to maximize bulb brightness under voltage limit. Measure currents and voltages, compare efficiencies. Present findings and redesign based on peer feedback.

Prepare & details

Explain how the drift velocity of electrons compares to the speed of the electric signal in a wire.

Facilitation Tip: During Design Challenge: Series-Parallel Efficiency, provide a fixed power supply and ask teams to justify their chosen configuration by calculating total resistance, current, and power output before building.

Setup: Groups at tables with access to research materials

Materials: Problem scenario document, KWL chart or inquiry framework, Resource library, Solution presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Teaching This Topic

Teach this topic by staging a narrative: start with energy transfer (potential difference), then measure its effect (current), and finally quantify opposition (resistance). Avoid analogies like water flow unless you immediately contrast them with drift velocity calculations. Research shows students retain understanding when they trace energy pathways with multimeters and build circuits themselves, not when they only watch demonstrations.

What to Expect

Successful learning shows when students can predict, measure, and justify changes in current, potential difference, and resistance across different circuit configurations. They should articulate how energy is conserved and where it transforms in a circuit.

Watch Out for These Misconceptions

Common Misconception

During Station Rotation: Ohm's Law Circuits, watch for students who believe current decreases as it passes through components like bulbs or resistors.

What to Teach Instead

Direct students to place ammeters at multiple points in the same series branch and observe that readings remain identical, reinforcing charge conservation through direct measurement.

Common Misconception

During Whole Class Demo: Signal vs Drift Speed, watch for students who think electrons move quickly through wires because the bulb lights instantly.

What to Teach Instead

Use a long transparent tube with small beads to show slow bead movement while signaling the far end instantly, then calculate drift velocity using measured current, wire length, and electron density to quantify the difference.

Common Misconception

During Pairs Investigation: Ohmic vs Non-Ohmic, watch for students who assume all components follow Ohm’s Law because voltage is present.

What to Teach Instead

Ask students to trace and measure voltage drops across each component in their circuits, then compare I-V graphs to observe where resistance changes and energy is transformed.

Assessment Ideas

Quick Check

After Station Rotation: Ohm's Law Circuits, ask students to solve a circuit problem involving an unknown resistor using Ohm’s Law and explain their steps to a partner.

Discussion Prompt

During Pairs Investigation: Ohmic vs Non-Ohmic, circulate and ask pairs to justify why their I-V graphs differ, focusing on resistance changes and energy transfer.

Exit Ticket

After Design Challenge: Series-Parallel Efficiency, have students submit a completed circuit diagram, calculated values for total resistance and current, and a brief explanation of their efficiency choice.

Extensions & Scaffolding

• Challenge: Ask advanced students to design a circuit that maintains constant current despite changes in supply voltage, using a variable resistor and explaining their strategy.
• Scaffolding: Provide pre-labeled circuit diagrams for students who struggle with construction, or assign roles within pairs to ensure both partners participate in measurement.
• Deeper: Introduce the concept of internal resistance by having students measure terminal potential difference across a power supply under different load conditions and graph the results.

Key Vocabulary

Current (I)	The rate of flow of electric charge, measured in amperes (A). It represents how much charge passes a point per second.
Potential Difference (V)	The energy transferred per unit of charge moving between two points in a circuit, measured in volts (V).
Resistance (R)	The opposition to the flow of electric current, measured in ohms (Ω). It determines how much current flows for a given potential difference.
Ohm's Law	A fundamental law stating that the current through a conductor between two points is directly proportional to the voltage across the two points, given constant temperature. Mathematically, V = IR.
Non-ohmic Component	A component whose resistance changes with the applied voltage or current, resulting in a non-linear I-V graph. Examples include filament lamps and diodes.