LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER

1 1 KS3 SCIENCE - PHYSICS KS3 SCIENCE - PHYSICS Magnetism

MAGNETIC FORCES & FIELDS 2 2

3 3 “Magnets” are things which create a force that attracts or repels objects “Magnets” are things which create a force that attracts or repels objects

MAGNETIC FORCES & FIELDS 4 4 “Magnets” are things which create a force that attracts or repels objects “Magnets” are things which create a force that attracts or repels objects Only certain magnetic materials are attracted by magnets Only certain magnetic materials are attracted by magnets

MAGNETIC FORCES & FIELDS 5 5 Steel can be magnetised permanently by stroking a magnet along it Steel can be magnetised permanently by stroking a magnet along it There are small magnetic regions or “Domains” in the steel, which are jumbled up to start with There are small magnetic regions or “Domains” in the steel, which are jumbled up to start with

MAGNETIC FORCES & FIELDS 6 6 Steel can be magnetised permanently by stroking a magnet along it Steel can be magnetised permanently by stroking a magnet along it Stroking with a magnet lines-up the domains, and we think that this is what makes a thing magnetic Stroking with a magnet lines-up the domains, and we think that this is what makes a thing magnetic

MAGNETIC FORCES & FIELDS 7 7 Some metals can be magnetised, or attracted by a magnet, others cannot Some metals can be magnetised, or attracted by a magnet, others cannot Magnetic metals include iron, steel, nickel and cobalt Magnetic metals include iron, steel, nickel and cobalt Other metals, wood, plastic etc. cannot be attracted by a magnet Other metals, wood, plastic etc. cannot be attracted by a magnet

MAGNETIC FORCES & FIELDS 8 8 Magnets create a “Magnetic Field” around them which runs from the “North Pole” to the “South Pole” Magnets create a “Magnetic Field” around them which runs from the “North Pole” to the “South Pole” N N S S

N N S S S S N N N N S S S S N N N N S S S S N N N N S S S S N N MAGNETIC FORCES & FIELDS 9 9 Magnetic forces can be felt anywhere within the magnetic field, but poles are the strongest parts of a magnet - like poles repel, unlike poles attract Magnetic forces can be felt anywhere within the magnetic field, but poles are the strongest parts of a magnet - like poles repel, unlike poles attract N N S S N N S S N N S S N N S S N N S S N N S S N N S S N N S S

MAGNETIC FORCES & FIELDS 10 The Earth also has a magnetic field, going from geographic South to geographic North The Earth also has a magnetic field, going from geographic South to geographic North

MAGNETIC FORCES & FIELDS 11 The Earth also has a magnetic field, going from geographic South to geographic North The Earth also has a magnetic field, going from geographic South to geographic North A bar magnet suspended horizontally will align with the Earth’s magnetic field like a compass A bar magnet suspended horizontally will align with the Earth’s magnetic field like a compass

ELECTROMAGNETS 12

ELECTROMAGNETS 13 A coil of wire with an electric current running through it generates a magnetic field - this is called a “Solenoid” A coil of wire with an electric current running through it generates a magnetic field - this is called a “Solenoid”

ELECTROMAGNETS 14 The coil becomes like a bar magnet with a strong magnetic field inside The coil becomes like a bar magnet with a strong magnetic field inside

ELECTROMAGNETS 15 The magnetic field is stronger if we increase the current through the coil The magnetic field is stronger if we increase the current through the coil

ELECTROMAGNETS 16 The magnetic field also becomes stronger if the coil has more turns The magnetic field also becomes stronger if the coil has more turns

ELECTROMAGNETS 17 The magnetic field is particularly strong with an iron bar inside the coil The magnetic field is particularly strong with an iron bar inside the coil

ELECTROMAGNETS 18 The end result is like a strong bar magnet and the position of the poles depends on the direction of the current The end result is like a strong bar magnet and the position of the poles depends on the direction of the current CURRENT

USES OF ELECTROMAGNETS 19

USES OF ELECTROMAGNETS 20 Using a solenoid with an iron bar inside can create a very strong magnetic force, and it can also be switched on and off Using a solenoid with an iron bar inside can create a very strong magnetic force, and it can also be switched on and off A good example is the use of an electro-magnet to pick up cars in a scrap yard A good example is the use of an electro-magnet to pick up cars in a scrap yard

USES OF ELECTROMAGNETS 21 Other examples include bells, which are used in schools to herd the children around Other examples include bells, which are used in schools to herd the children around Electro magnets pull the arm, this movement then breaks the circuit so the arm is released again Electro magnets pull the arm, this movement then breaks the circuit so the arm is released again