Science · Year 7 · Forces in Action · Summer Term

Magnets and Electromagnets: Invisible Forces

Exploring the properties of magnets and how electricity can create magnetism.

• National Curriculum Attainment Targets
• KS3: Science - Electricity and Magnetism

About This Topic

Magnets create invisible forces that pull or push on magnetic materials like iron and steel. Year 7 students discover that every magnet has a north pole and a south pole. Like poles repel each other, while unlike poles attract. They map magnetic fields around bar magnets using compasses or iron filings, which reveal curved field lines from pole to pole. This leads to electromagnets, formed by wrapping insulated wire around an iron core and passing an electric current through the coil. The magnetic force depends on the number of coils, current strength, and core material.

This topic fits the KS3 Electricity and Magnetism standards within the Forces in Action unit. Students design fair tests to compare electromagnet strengths, control variables, and record data on lifting power or picking up paperclips. These skills build experimental design and analysis abilities, essential for scientific method. Connections to real-world uses, such as in electric motors or doorbells, show practical relevance.

Active learning suits this topic because forces are not visible, so hands-on manipulation provides direct evidence. Students building and testing electromagnets see immediate results from changes, which confirms predictions and corrects ideas through trial. Group work on field plotting encourages shared observations and discussion, deepening understanding and engagement.

Key Questions

1. Explain how magnets attract and repel each other.
2. Analyze the factors that affect the strength of an electromagnet.
3. Design an experiment to investigate the magnetic field around a bar magnet.

Learning Objectives

• Explain the attraction and repulsion between magnetic poles using the concept of magnetic fields.
• Analyze the relationship between the number of coils, current strength, and core material on the strength of an electromagnet.
• Design and conduct a fair test to investigate how changing one variable (e.g., number of coils) affects the strength of an electromagnet.
• Compare the magnetic field patterns of different types of magnets (e.g., bar, horseshoe) using observational data.

Before You Start

Basic Electrical Circuits

Why: Students need to understand the concept of electric current flowing through a wire to comprehend how it generates a magnetic field in an electromagnet.

Properties of Matter

Why: Familiarity with different materials, particularly magnetic and non-magnetic substances, is helpful for understanding which materials are affected by magnets and which can be used as cores.

Key Vocabulary

Magnetic Field	The area around a magnet where its magnetic force can be detected. It is often visualized with lines showing the direction and strength of the force.
Electromagnet	A temporary magnet created by passing an electric current through a coil of wire wrapped around a magnetic core, such as iron.
Magnetic Pole	The two ends of a magnet, designated North and South, where the magnetic force is strongest and where magnetic field lines emerge or enter.
Attract	The force that pulls two objects together. In magnetism, unlike poles (North and South) attract each other.
Repel	The force that pushes two objects apart. In magnetism, like poles (North and North, or South and South) repel each other.

Watch Out for These Misconceptions

Common Misconception

Magnets attract all metals.

What to Teach Instead

Magnets only attract ferromagnetic materials like iron, steel, nickel, cobalt. Active sorting activities with metal samples let students test and classify, revealing patterns through group discussion and data tables.

Common Misconception

Electromagnets stay magnetic after current stops.

What to Teach Instead

The field exists only while current flows; it disappears when switched off. Hands-on switching demos with immediate tests on paperclips show this clearly, helping students revise models via repeated observation.

Common Misconception

More coils always make stronger magnet, regardless of current.

What to Teach Instead

Both coils and current matter. Paired experiments varying one factor at a time demonstrate interactions, with graphing results to spot combined effects during class analysis.

Active Learning Ideas

Stations Rotation: Magnet Properties Stations

Prepare four stations: pole identification with hanging magnets, attract/repel tests with various materials, field plotting with iron filings, and compass tracing around a bar magnet. Groups rotate every 10 minutes, sketching observations and noting patterns at each station. Conclude with a class share-out of findings.

45 min·Small Groups

Pairs: Build and Test Electromagnets

Provide coils, iron nails, batteries, and wires. Pairs wind different numbers of coils, connect to circuit, and test lifting paperclips. They record results in a table, then swap to try varying battery voltage. Discuss which factor has greatest effect.

30 min·Pairs

Small Groups: Fair Test Design Challenge

Groups design experiment to investigate one factor on electromagnet strength, such as core material. They predict, list equipment, control variables, and test three options. Present method and results to class for peer feedback.

50 min·Small Groups

Whole Class: Field Visualisation Demo

Sprinkle iron filings near bar magnets on white paper, tap gently to align. Project under document camera. Students draw field lines, then repeat with electromagnet switched on/off to compare. Note safety with currents.

20 min·Whole Class

Real-World Connections

• Engineers at scrapyards use powerful electromagnets on cranes to lift and sort large quantities of iron and steel, demonstrating the practical application of controlling magnetic force.
• Medical professionals use MRI (Magnetic Resonance Imaging) scanners, which rely on strong magnetic fields generated by superconducting electromagnets, to create detailed images of the inside of the human body for diagnosis.
• Manufacturers of electric doorbells and simple electric motors utilize the principle of electromagnetism to convert electrical energy into mechanical motion.

Assessment Ideas

Exit Ticket

Provide students with a diagram showing a bar magnet and a compass. Ask them to draw the magnetic field lines around the magnet and label the North and South poles. Then, ask them to write one sentence explaining why the compass needle points in a specific direction.

Quick Check

Present students with three electromagnets, each with a different number of coils (e.g., 20, 50, 100) but the same current. Ask them to predict which electromagnet will be strongest and explain their reasoning based on the factors discussed. Then, have them test their predictions by seeing how many paperclips each can lift.

Discussion Prompt

Pose the question: 'How could you design an experiment to determine if the type of core material (e.g., iron vs. plastic) affects the strength of an electromagnet?' Facilitate a class discussion, guiding students to identify variables to control and measure.

Frequently Asked Questions

What factors affect electromagnet strength?

Key factors are number of wire coils, electric current strength, and iron core material. Students find more coils or higher current increase strength by amplifying the magnetic field. Soft iron cores work best as they magnetise easily. Fair testing activities isolate one variable, such as using identical batteries while changing coils from 20 to 100, to measure lifting power clearly.

How to teach magnetic poles and forces?

Use bar magnets to show like poles repel, unlike attract. Hang magnets on string for free movement demos. Compass work around poles traces field direction. Stations let students explore freely, building intuition before diagrams. This links to field lines as paths of force.

How can active learning help students understand magnets and electromagnets?

Active learning counters invisibility of forces with tactile experiences. Building electromagnets gives instant feedback on variables, boosting confidence in predictions. Group field plotting with iron filings sparks collaborative talk, refining concepts. These methods improve retention over lectures, as students connect actions to outcomes in safe, engaging ways.

What experiments for magnetic fields in Year 7?

Plot fields with compass needles around bar magnets, marking north-pointing directions for lines. Iron filings on paper show dense lines between poles. Compare permanent magnet to electromagnet fields. Students sketch, measure distances, and discuss force strength variations, aligning with fair testing skills.