Physics · Grade 12

Active learning ideas

Magnetic Fields from Currents

Active learning works well for magnetic fields from currents because students can directly observe how moving charges create forces and fields. Seeing a compass needle move or iron filings form patterns helps turn abstract ideas into concrete evidence, making the invisible visible and the unfamiliar familiar.

• Ontario Curriculum Expectations
• HS.PS2.B.1

• 30–50 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Simulation Game
• 30 min · Pairs

Demonstration: Compass Around Wire

Secure a straight wire vertically and pass current through it from a low-voltage supply. Place a compass nearby at various distances and angles. Students record deflection angles and sketch field lines, applying the right-hand rule to verify direction.

Explain how moving charges create magnetic fields.

Facilitation Tip

During the compass demonstration, position yourself so all students can see the needle’s deflection, then pause after each current change to ask students to predict the next movement.

What to look for

Provide students with diagrams of current-carrying wires and solenoids with current directions indicated. Ask them to draw the magnetic field lines and indicate their direction using the right-hand rule. For solenoids, ask them to predict where the field is strongest.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 02

• Collaborative Problem-Solving
• 45 min · Small Groups

Collaborative Problem-Solving: Iron Filings and Solenoid

Wind copper wire around a tube to make a solenoid connected to a battery. Sprinkle iron filings on paper over the solenoid and tap gently. Students photograph patterns before and after inserting an iron core, noting changes in field concentration.

Analyze the direction and strength of magnetic fields around current-carrying wires.

Facilitation Tip

For the iron filings and solenoid lab, assign roles like photographer, filament handler, and recorder to keep students engaged and accountable during rotations.

What to look for

Pose the question: 'How does the magnetic field created by a solenoid differ from the magnetic field created by a single loop of wire carrying the same current? What makes the solenoid's field more useful in certain applications?'

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

Activity 03

• Inquiry Circle
• 50 min · Small Groups

Inquiry Circle: Field Strength Variation

Use a plotting compass or Hall probe to map field strength around a current-carrying wire at fixed distances. Vary current and record data in tables. Groups graph results to confirm inverse square relationship and discuss sources of error.

Construct a model to demonstrate the magnetic field of a solenoid.

Facilitation Tip

In the field strength variation inquiry, provide graph paper and rulers so students can plot data precisely and spot patterns in the spacing of their points.

What to look for

Ask students to write down the formula for the magnetic field strength near a long, straight wire. Then, have them explain in one sentence how increasing the current would affect this field strength.

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

Activity 04

• Simulation Game
• 40 min · Pairs

Build: Electromagnet Model

Provide wire, nails, and batteries for students to construct solenoids. Test lifting power with paperclips at different turns and currents. Pairs compare designs and predict improvements based on field strength principles.

Explain how moving charges create magnetic fields.

Facilitation Tip

When students build electromagnet models, circulate with a multimeter to help them measure field strength and relate it to coil turns and current in real time.

What to look for

Provide students with diagrams of current-carrying wires and solenoids with current directions indicated. Ask them to draw the magnetic field lines and indicate their direction using the right-hand rule. For solenoids, ask them to predict where the field is strongest.

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

A few notes on teaching this unit

Teaching magnetic fields from currents benefits from a mix of guided discovery and student-led modeling. Start with the compass demonstration to establish that currents create fields, then use the solenoid lab to contrast internal and external fields. Avoid relying solely on diagrams; hands-on experience helps students build accurate mental models. Research shows that combining tactile experiments with immediate discussion strengthens spatial reasoning about field lines.

Successful learning looks like students confidently using the right-hand rule to predict field direction, explaining why field strength changes with distance and current, and distinguishing between fields inside and outside a solenoid. They should also connect their observations to Ampere's law through careful modeling and discussion.

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Watch Out for These Misconceptions

• During Demonstration: Compass Around Wire, watch for students who assume magnetic fields only come from permanent magnets. Redirect by asking them to note how the compass deflects only when the wire carries current, tying the observation to moving charges and Oersted’s discovery.

  During Demonstration: Compass Around Wire, have students record the compass needle’s behavior before, during, and after current flows. Ask them to compare their observations with images of bar magnets to highlight the difference between static and dynamic sources.

• During Demonstration: Compass Around Wire, watch for students who believe the field direction is arbitrary or always clockwise. Redirect by asking them to use the right-hand rule on their own compass maps and compare with peers.

  During Demonstration: Compass Around Wire, provide plotting compasses and ask pairs to sketch the field pattern around the wire. Have them use the right-hand rule to label their sketches and present their findings to the class.

• During Lab: Iron Filings and Solenoid, watch for students who assume the magnetic field is equally strong everywhere inside the solenoid. Redirect by asking them to observe where filings cluster most densely and relate that to field strength.

  During Lab: Iron Filings and Solenoid, instruct students to sketch the field lines inside and outside the solenoid on paper, marking areas of high and low density. Ask them to explain why the pattern changes along the axis and at the ends.

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Methods used in this brief

• Simulation Game
• Collaborative Problem-Solving
• Inquiry Circle