Transcript Read the notes, then answer the questions on the last slide.

Read the notes, then answer
the questions on the last slide.
Magnets
• Magnets attract steel, iron, nickel and cobalt.
• Two north poles repel
N N
• Two south poles repel
S S
• A north and a south pole
attract
N
S
Magnetic Fields - 1
• The field around one
magnet.
• The field between two north
poles.
• The field between a north
and a south pole.
Magnetic Fields - 2
• The field around a
current carrying wire.
• The field around a
current carrying coil
looks the same as
around a bar magnet.
Electromagnets
• Complete the circuit below and the nail
becomes magnetic.
• The strength of an electromagnet
increases with its current.
• The strength of an electromagnet
depends on the number of turns- more
turns makes a stronger magnet.
• The strength of an electromagnet
increases greatly if it has a soft iron
core.
Uses of Electromagnets
• Very large electromagnets are used in scrap
yards to lift car bodies.
• Very small electromagnets are used in video
players and tape recorders to wipe, record and
read the programmes.
• Many loudspeakers and motors contain
electromagnets.
Bell
• When you press on a bell switch, electricity
flows through an electromagnet.
• This attracts an iron armature which
causes the hammer to hit the bell.
• This also breaks the circuit, switching off
the electromagnet.
• So the armature springs back to its original
position and so on.
Relay
• A relay is a device used
in electronics to switch
on circuits carrying
heavy currents.
Questions
• 1. Name two metals that are magnetic.
• 2. Name two metals that aren’t magnetic.
• 3. True or False – South and North Poles
repel.
• 4. Name two uses of an electromagnet.
• 5. Name two ways of increasing the
strength of an electromagnet.