KS4 Electricity - Electromagnetism

What is a magnetic field? Where would you find a magnetic field?

strongest field at poles Magnetic field Around every magnet is an invisible force field that will affect all magnetic objects inside it. The magnetic field of a bar magnet is seen with iron filings. strongest field at poles N S What does the magnetic field around a bar magnet look like? Where is the magnetic field strongest?

What materials will stick to magnets? Look around the laboratory or your teacher will provide a tray. See which materials will stick to a magnet and which materials will not. Magnetic materials Non-magnetic materials

What materials will magnets stick to? Magnets and materials What materials are magnets made from? Iron or steel. N S What materials will magnets stick to? Iron or steel. And nickel!

Forces between magnets – experiment

Repulsion and attraction Repel/attract Repel/attract Repel/attract Unlike poles attract. Like poles repel.

Separating coins How could you separate steel and gold coins using a magnet? N S Steel coins would stick to magnet, gold coins would be left behind.

What does the magnetic field for a bar magnet look like? In what direction do magnetic field lines point? N North to South S

Revising magnetism I Iron or steel Magnets are made from which materials? ___________ The Poles What are the ends of a magnet called? __________ What do we call the area around a magnet where a magnetic force exists? __________________ The Magnetic Field Pull together What does the word attract mean? __________ What does the word repel mean? __________ Push apart

Revising magnetism II Repel What will two north poles do if brought together? _____ Repel What will two south poles do if brought together? ______ Repel What will a north and a south pole do if brought together? _______ Attract Iron and steel What materials are attracted by magnets? ___________ Is magnetism a contact or non-contact force? _________ Non-contact

Electromagnets A coil of wire acts like a bar magnet when it has an electric current flowing through it. One end of the coil becomes a north-seeking pole. One end of the coil becomes a south seeking pole. This is called an electromagnet.

Making an electromagnet: Apparatus: Batteries Wire Iron Nail What to do: Wrap a coil of wire around the iron nail. Connect the coil of wire to the batteries. See how many paperclips you can pick up.

Results How many paperclips could you pick up? Can you think of any ways to make the electromagnet pick up more paperclips? More batteries (more current) Number of paperclips Number of batteries More turns of wire on the coil Number of paperclips Number of turns

Electromagnetic strength – experiment

Electromagnetic strength - results The results for the number of drawing pins attracted to the electromagnet with no core are: 1 2 3 4 6 8 12 18 number of cells number of coils How does changing the current affect the strength of an electromagnet? How does changing the number of coils affect the strength of an electromagnet?

Electromagnetic strength - results Compare the results for the number of drawing pins attracted to the electromagnet with no core and an iron core: 1 2 3 4 6 8 12 18 number of cells 1 2 3 4 6 8 10 12 16 22 number of cells number of coils number of coils What effect does an iron core have on the strength of an electromagnet?

Electromagnetic strength - results Compare the results for the number of drawing pins attracted to the electromagnet with no core and a copper core: 1 2 3 4 6 8 12 18 number of cells 1 2 3 4 6 8 12 18 number of cells number of coils number of coils What effect does a copper core have on the strength of an electromagnet?

Ways to make an electromagnet stronger There are three ways to make an electromagnet stronger. Do you know them? ___________________ More turns on the coil More electrical current Using an iron core S S N What happens if you turn the battery around in an electromagnet? The poles on the coil reverse, north becomes south and south becomes north.

 Attract and repel Attract Repel Stick together What do like poles do? Attract and repel Attract Repel Stick together 

Which material below will not stick to a magnet? Steel paper clip Aluminium can Iron nail Steel key 

Which of the below will not increase the strength of an electromagnet? More coils More current Less current Iron core 

In which direction do magnetic field lines always point? East to west West to east South to north North to south 

Which of the following is not a use of electromagnets? Fridge magnets Loud speakers Relays Circuit breakers 