Topicm8e24c48e86580c21_1528449000663_0Topic

Electromagnets and their application

Levelm8e24c48e86580c21_1528449084556_0Level

Second

Core curriculumm8e24c48e86580c21_1528449076687_0Core curriculum

VII. Magnetism. The student:

5) describes the structure and operation of the electromagnet; describes the interaction of electromagnets and magnets; lists examples of the use of electromagnets.

Timingm8e24c48e86580c21_1528449068082_0Timing

45 minutes

General learning objectivesm8e24c48e86580c21_1528449523725_0General learning objectives

Describes how an electromagnetelectromagnetelectromagnet works.

Key competencesm8e24c48e86580c21_1528449552113_0Key competences

1. Builds a simple electromagnet.

2. Identifies the properties of an electromagnet.

Operational (detailed) goalsm8e24c48e86580c21_1528450430307_0Operational (detailed) goals

The student:

- explains and presents the operation of the electromagnet,

- examines the interaction of electromagnets and magnets,

- describes the use of electromagnets.

Methodsm8e24c48e86580c21_1528449534267_0Methods

1. Discussion.

2. Experiment.

Forms of workm8e24c48e86580c21_1528449514617_0Forms of work

1. Individual work.

2. Group work.

Lesson stages

Introductionm8e24c48e86580c21_1528450127855_0Introduction

Answer the introductory questions for the lesson:

1. Is the conductor with the current a source of magnetic field?

2. How can you check if the conductor with the current is the source of the magnetic field?

A magnetic needle parallel to the guide was placed under or over the conductor. What will happen to the magnetic needle when the current is turned on?

Procedurem8e24c48e86580c21_1528446435040_0Procedure

The teacher introduces the concept of electromagnets.

Electromagnet - a device that generates a magnetic field as a result of electric current passing through it. The magnetic field around the electromagnet exists as long as the current flows. Electromagnets usually consist of an iron core and wire wound in the form of coils around this core.

A simple electromagnet can be formed by means of a wire coil wound around an iron core, e.g. a large nail.

[Interactive graphics]

Experiment 
Properties of an electromagnet.

Problem: 
What properties a simple electromagnet has?

Hypothesis: 
Electromagnet strength depends on its magnetic field.

Materials:  
- battery 4,5 V, 
- thin insulated copper wirewirewire, 
- nail, 
- compass, 
- iron filings, 
- paper clips.

Procedure:

1. Wind 50 turns of insulated wire around an iron nail. Leave enough wire free at both ends to make connections to the battery.

2. Connect the ends of the wire to the battery.

3. To find out if the nail became a magnet, test it with iron filings. What happens if you disconnect the battery?

4. Place the compass needle near the electromagnetelectromagnetelectromagnet. Determine its poles.

5. Find out how many paper clips your electromagnet can attract.

6. Wind now 100 turns of insulated wirewirewire around an iron nail. Find out how many paper clips your electromagnet can attract now.

Conclusion: 
If the battery is disconnected, there is no more magnetic fieldmagnetic fieldmagnetic field around the nail. The more wire loops are wound on the nail, the stronger is the magnetic field.

How electromagnets work:

To get an electromagnet working the voltage must be applied to the coilcoilcoil. The electric currentcurrentcurrent begins to flow and forms the magnetic field around the wirewirewire. One end of the coil is a north pole and the other end is a south pole. The iron coreiron coreiron core reinforces this field.

The shape of the magnetic field lines around the electromagnet is the same as the field lines around the bar magnet. The location of the poles and hence the direction of the magnetic field can be reversed by swapping the battery terminals.

An electromagnetelectromagnetelectromagnet is not a permanent magnet. If the voltage supply is off there is no magnetic fieldmagnetic fieldmagnetic field anymore.

Properties of electromagnet:

An electromagnet can be stronger if:

- an ironiron coreiron core is put inside the coilcoilcoil,
- more turns are added to the coil,
- the currentcurrentcurrent flowing through the coil is increased.

[Illustration 1]

Electromagnets vs permanent magnets:

Both electromagnets and permanent magnets are the sources of the magnetic field. Both are dipoles, which means they have a north and south pole, but only electromagnets can switch its poles, by reversing the voltage. The strength of an electromagnet can vary while in case of permanent magnet it stays the same.m8e24c48e86580c21_1527752256679_0Both electromagnets and permanent magnets are the sources of the magnetic field. Both are dipoles, which means they have a north and south pole, but only electromagnets can switch its poles, by reversing the voltage. The strength of an electromagnet can vary while in case of permanent magnet it stays the same.

Use of electromagnets:

Nowadays, there are many various applications of electromagnets. They are used in countless number of electric devices, including motors, generators, relays, etc. There are broadly use in industry, e.g. in scrap yards to pick up heavy cars, medicine e.g. MRI machines, science, e.g. accelerators, and in devices we use in daily life, e.g. hard disc drives, doorbells, speakers, induction kitchen, CD players.m8e24c48e86580c21_1527752263647_0Nowadays, there are many various applications of electromagnets. They are used in countless number of electric devices, including motors, generators, relays, etc. There are broadly use in industry, e.g. in scrap yards to pick up heavy cars, medicine e.g. MRI machines, science, e.g. accelerators, and in devices we use in daily life, e.g. hard disc drives, doorbells, speakers, induction kitchen, CD players.

Lesson summarym8e24c48e86580c21_1528450119332_0Lesson summary

A type of magnet in which the magnetic fieldmagnetic fieldmagnetic field is produced by an electric currentcurrentcurrent is called electromagnetelectromagnetelectromagnet. The magnetic field around the electromagnet depends on the current flowing through the coilcoilcoil, on the number of turns and on whether it has an iron coreiron coreiron core. The magnetic field around an electromagnet disappears when the currentcurrentcurrent is turned off.

Selected words and expressions used in the lesson plan

coilcoilcoil

currentcurrentcurrent

electromagnetelectromagnetelectromagnet

iron coreiron coreiron core

looplooploop

magnetic fieldmagnetic fieldmagnetic field

wirewirewire