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SECTION 6: MAGNETISM AND ELECTROMAGNETISM Chapter 21 Magnetism and Electromagnetism

SECTION 6: MAGNETISM AND ELECTROMAGNETISM

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SECTION 6: MAGNETISM AND ELECTROMAGNETISM. Chapter 21 Magnetism and Electromagnetism. Magnets attract magnetic materials but not non-magnetic materials. Magnetism is a non-contact force (acts at a distance). Magnetic materials:. iron. steel. nickel. cobalt. - PowerPoint PPT Presentation

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Page 1: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

SECTION 6: MAGNETISM AND

ELECTROMAGNETISM

Chapter 21Magnetism and

Electromagnetism

Page 2: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

Magnets attract magnetic materials but not non-magnetic materials.Magnetism is a non-contact force (acts at a distance).

Magnetic materials:• iron• steel• nickel• cobalt

The region around a magnet where a magnetic force can be felt is called the magnetic field.The magnetic field is strongest at the poles of a magnet.

Page 3: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

north-seeking pole or

north pole

south-seeking pole or

south pole

Like poles

repel

Unlike poles attract

Page 4: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

REPULSION

ATTRACTION

REPULSION

ATTRACTION

S

SS

S

S

S S

S

N N

NN

NN

N N

Page 5: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

A magnetic field around a bar magnet has a shape and direction.

The magnetic field is represented using magnetic field lines (lines of force, flux lines) that show the shape, direction and strength of the field.

Page 6: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

Investigate the shape of the magnetic field between two bar magnets.

A

B

C D

N

N

N

NN

N

N

N S

S

S

S S

S

S

Page 7: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

N S

UNIFORM MAGNETIC FIELD.

Magnetic field lines are parallel and equally spaced apart.

Page 8: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

PERMANENT MAGNETS TEMPORARY MAGNETS

Made from magnetically hard materials, such as steel.

Retain their magnetism once they have been magnetised.

Made from magnetically soft materials, such as iron.

They are easy to magnetise but lose their magnetism easily.

Magnetism can be induced in some materials when they are placed in a magnetic field.

Page 9: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

ElectromagnetismA wire carrying a current has a magnetic field around it.

The magnetic field around a current carrying wire has a circular shape.

Page 10: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

The right hand grip rule

Page 11: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

The magnetic field around a flat coil

Page 12: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM
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SolenoidsThe magnetic field around a solenoid has the same shape as the field around a bar magnet.

The field inside the solenoid is very strong and uniform. It can be used to magnetise objects.

Page 15: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

Polarity of a coil

Page 16: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

The strength of the magnetic field around a solenoid can be increased by:

• Increasing the current.• Increasing the number of turns on the

solenoid.• Using a magnetically soft core such as

iron.• Bringing the poles together.

Page 17: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

Using electromagnets

Page 18: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

The electric bell

Page 19: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

Circuit breaker

Page 20: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

An electromagnetic door lock

There is an iron bar keeping the door locked.If the security officer agrees to let you in, he presses a switch which allows a current to flow through the solenoid.

What happens to the iron bar?

Page 21: SECTION 6:  MAGNETISM AND ELECTROMAGNETISM

The electromagnetic relay