# KS4 Physics Electromagnetism.

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KS4 Physics Electromagnetism

Electromagnetism Magnets Magnetic fields Electromagnets
Contents Electromagnetism Magnets Magnetic fields Electromagnets Summary activities

Magnetic or non-magnetic?
A magnetic material is attracted to magnets and can be made into a magnet. N S Investigate different materials to find out which are attracted to a magnet and record your results in a table. Magnetic materials Non-magnetic materials Which materials are attracted to a magnet? iron, steel, cobalt and nickel

Using magnets to separate coins
How can a magnet be used to separate coins made from steel and coils made from gold? N S Steel coins are attracted to a magnet but gold coins are not.

iron, steel, cobalt and nickel
Magnetic materials What materials can magnets be made from? N S iron, steel, cobalt and nickel Iron is easy to magnetise and also loses its magnetism easily. Iron is called a soft magnetic material. Steel is harder to magnetise but does not lose its magnetism easily. Steel is called a hard magnetic material. Magnets are usually made of steel and other hard magnetic materials because they can retain their magnetism.

Electromagnetism Magnets Magnetic fields Electromagnets
Contents Electromagnetism Magnets Magnetic fields Electromagnets Summary activities

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

Magnetic field of a bar magnet
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?

Forces between magnets – experiment

Repulsion and attraction
repel/attract N S S N repel/attract S N S N repel/attract Unlike poles attract. Like poles repel.

1. Magnets are made from which materials? ____________
Revising magnetism (1) 1. Magnets are made from which materials? ____________ iron or steel 2. What are the ends of a magnet called? ________ poles 3. What do we call the area around a magnet where a magnetic force exists? _______________ magnetic field 4. What does the word attract mean? _____________ pull together 5. What does the word repel mean? _____________ push apart

6. What will two north poles do if brought together? ______
Revising magnetism (2) 6. What will two north poles do if brought together? ______ repel 7. What will two south poles do if brought together? ______ repel 8. What will a north pole and a south pole do if brought together? _______ attract 9. What materials are attracted by magnets? _____________ iron and steel 10. Is magnetism a contact or non-contact force? ___________ non-contact

Electromagnetism Magnets Magnetic fields Electromagnets
Contents Electromagnetism Magnets Magnetic fields Electromagnets Summary activities

What is an electromagnet?
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 (N pole). One end of the coil becomes a south seeking pole (S 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 the electromagnet can pick up. Results: How many paperclips could the electromagnet pick up? How could the electromagnet pick up more paperclips?

Investigating electromagnets – experiment

Investigating electromagnets – results (1)
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?

Effect of increasing the current
Increasing the number of cells, increases the current, and the number of paperclips picked up by the electromagnet also increases. x The strength of the magnetic field increases as the current flowing through the coil increases. x x Number of paperclips x x x x x Current (amps)

Effect of increasing the number of coils
Increasing the number of turns on the coil, increases the number of paperclips picked up by the electromagnet. x x The strength of the magnetic field increases as the number of turns on the coil increases. x Number of paperclips x x x x x Number of turns

Investigating electromagnets– results (2)
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?

Investigating electromagnets – results (3)
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?

Electromagnets – summary
There are three ways to make an electromagnet stronger. What are they? ____________________ More turns on the coil More electrical current Using an iron core S N What happens if the position of the battery in the electromagnet circuit is reversed? The poles on the coil also reverse – north becomes south and south becomes north. N S

Electromagnetism Magnets Magnetic fields Electromagnets
Contents Electromagnetism Magnets Magnetic fields Electromagnets Summary activities

Glossary core – An object, usually made of iron, which is placed inside the coil of an electromagnet and increases the strength of the magnetic field. electromagnet – A coil of wire that produces a magnetic field when a current is passed through it. hard magnetic material – A material that is hard to magnetise but does not lose its magnetism easily. magnetic field – The invisible force field around a magnet or electromagnet that will affect all magnetic objects within that area. poles – The parts of a magnet where the magnetic field is strongest. soft magnetic material – A material that is easy to magnetise and also loses its magnetism easily.

Anagrams

Multiple-choice quiz