Physics · Secondary 3

Active learning ideas

Magnetic Field of a Current

Active learning works for this topic because students need to see how invisible magnetic fields behave around current-carrying wires and solenoids. Hands-on mapping and rule application help them connect abstract concepts to measurable, visual evidence in real time.

• MOE Syllabus Outcomes
• MOE: Electricity and Magnetism - S3
• MOE: Electromagnetism - S3

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Plan-Do-Review
• 30 min · Small Groups

Compass Mapping: Wire Fields

Connect a straight wire to a low-voltage DC supply. Students position a compass at points around the wire, note needle deflection, and sketch field lines. Repeat with reversed current to confirm right-hand grip rule.

Explain how a current-carrying wire produces a magnetic field around it.

Facilitation Tip

During Compass Mapping, position compasses close but not touching the wire to avoid interference from the compass’s own magnetism.

What to look for

Present students with diagrams of current-carrying wires and solenoids with varying current directions. Ask them to draw the magnetic field lines and label the direction using the right-hand grip rule. Check for accurate application of the rule.

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

Activity 02

• Plan-Do-Review
• 45 min · Pairs

Solenoid Comparison Stations

Prepare solenoids with 20, 50, and 100 turns, plus iron core versions. Groups measure field strength using a compass deflection angle or Hall probe at center. Tabulate results and graph against turns or current.

Analyze the factors that affect the strength of the magnetic field produced by a solenoid.

Facilitation Tip

At Solenoid Comparison Stations, ensure students record current, number of turns, and field direction in a shared data table for group analysis.

What to look for

Pose the question: 'How could you design an experiment to determine if increasing the number of coils in a solenoid has a greater effect on magnetic field strength than increasing the current?' Facilitate a discussion on experimental design, variable control, and data collection.

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

Activity 03

• Plan-Do-Review
• 35 min · Pairs

Right-Hand Rule Relay

Set up stations with wires carrying current in varied directions. Pairs grip with right hand, predict field at test points, verify with compass. Switch roles and discuss errors as a class.

Predict the direction of the magnetic field around a straight wire using the right-hand grip rule.

Facilitation Tip

For the Right-Hand Rule Relay, move between groups quickly to correct hand orientation errors before they become habitual.

What to look for

Provide students with a scenario: 'A student wraps wire around a nail to create an electromagnet. What are two ways they could make the electromagnet stronger?' Students write their answers, demonstrating understanding of factors affecting solenoid field strength.

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

Activity 04

• Plan-Do-Review
• 25 min · Whole Class

Iron Filings Demo: Solenoid Fields

Place solenoids on paper sheets, sprinkle iron filings while current flows. Tap gently to align filings, photograph patterns. Students label poles and compare to bar magnet.

Explain how a current-carrying wire produces a magnetic field around it.

Facilitation Tip

In the Iron Filings Demo, use a thin layer of filings on a transparency over the solenoid to clearly show internal field patterns without obscuring the wires.

What to look for

Present students with diagrams of current-carrying wires and solenoids with varying current directions. Ask them to draw the magnetic field lines and label the direction using the right-hand grip rule. Check for accurate application of the rule.

• Remember
• Apply
• Analyze
• Self-Management
• Decision-Making
• Self-Awareness

A few notes on teaching this unit

Teachers often introduce this topic by first having students observe compass deflections near a straight wire to establish that currents create magnetic fields. Research suggests avoiding prolonged lecturing about the right-hand rule without immediate practice, as students may default to memorizing without understanding. Encourage students to articulate their observations aloud to reinforce connections between current direction, field lines, and compass behavior.

Successful learning looks like students accurately predicting magnetic field direction using the right-hand grip rule, distinguishing between wire and solenoid fields, and explaining how coil turns and current affect field strength. They should also troubleshoot misconceptions with peer feedback during activities.

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Watch Out for These Misconceptions

• During Compass Mapping: Wire Fields, watch for students attributing compass deflections to hidden magnets or external influences.

  Ask students to reverse the current direction and observe if the compass deflection reverses too, proving the field is linked to the wire’s current, not an external magnet.

• During Right-Hand Rule Relay, watch for students using the left hand or pointing the thumb toward magnetic north instead of the current direction.

  Have students physically grip a wire with the correct hand, align their thumb with the current direction shown on a labeled diagram, and observe the resulting field on a nearby compass for immediate feedback.

• During Solenoid Comparison Stations, watch for students assuming field strength depends only on current and not on coil turns.

  Ask groups to compare solenoids with the same current but different turn counts, then pool data to graph field strength versus turns and identify the proportional relationship.

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Methods used in this brief

• Plan-Do-Review