1. Cosmic Rays
Cosmic rays are very high energy particles
Most cosmic rays come from outer space, outside our solar system
1 % of cosmic rays are high energy electrons
99 % are the nuclei of atoms which have been stripped of their electrons

2. Where do Cosmic Rays Come From?
Some cosmic rays come from explosions taking place inside our own Sun
The majority of cosmic rays come from outside our solar system
- most of these cosmic rays are formed as dying stars explode to form supernovas
- some high energy cosmic rays may be produced by quasars
Some cosmic rays are as old as the Universe itself – they were produced by Big Bang 14.5 billion years ago
Explosions inside the Sun produce cosmic rays
Supernovas produce cosmic rays

3. Are Cosmic Rays Dangerous?
High energy cosmic rays can damage humans
High energy cosmic rays can damage DNA. This can lead to cancer and cause birth defects
Cosmic rays can damage the eyes causing cataracts. A cataract is where the lens of the eye becomes cloudy. This can cause blindness
Cosmic rays can also damage the nervous system. This can affect behaviour and may increase the risk of Alzheimer’s disease

4. Should I worry about Cosmic Rays?
Most galactic cosmic rays have too little energy to pass through the Earth’s atmosphere
The magnetic field of the Sun and the Earth bend the path of the cosmic rays so they are re-directed away from us
Outside of the Earth’s magnetic field we have less protection from cosmic rays. Cosmic rays are a serious health risk for astronauts

5. The Earth’s Magnetic Field
The Earth’s core is made of iron
The outer is made of molten (liquid) iron
As the liquid iron core moves around, it produces electrical currents
Electrical currents in the core produce the Earth’s magnetic field
The movement of the core is powered by convection currents in the molten iron
Without the Earth’s magnetic field, cosmic rays would destroy the ozone layer that protects us from the Sun’s UV light
Electrical currents in the Earth’s molten iron outer core produce a magnetic field

6. Compasses
The Earth has its own magnetic field
A freely swinging magnet will line up with the Earth’s magnetic field so it ends up pointing in a North-South direction
The needle of a compass is also a magnet. The needle can rotate easily. This allows the magnet to line up with the Earth’s magnetic field

7. The Northern Lights
The Northern Lights is a natural light display in the atmosphere close to the North Pole
The Earth’s magnetic field bends cosmic rays towards the poles
Cosmic rays hit the atmosphere near the North Pole
Cosmic excite molecules in the atmosphere causing them to produce light

8. Loudspeakers
Loudspeakers use electromagnets magnets to produce sound
The important parts of the loudspeaker are:
The CORE – this is a piece of iron or a permanent magnet
The COIL
The CONE

9. How a loudspeaker works
The CONE of the loudspeaker vibrates to produce sound
The COIL acts as an electromagnet that makes the cone vibrate
As the current in the coil changes, the magnetic field produced by the coil gets stronger and weaker
The coil pulls on the CORE, so the coil moves backwards and forwards
The core is attached to the CONE so the moving core makes the cone VIBRATE

10. MRI Scanners
MRI scanners are used to look inside the human bodies
MRI scanners use very powerful electromagnets to produce detailed pictures of our organs
MRI stands for Magnetic Resonance Imaging

11. Using Electromagnets
Electromagnets are useful because they can be switched on and off
Powerful electromagnets are used in scrap yards to move objects made of steel and iron – like cars
The electromagnet is switched ON to pick objects up
The electromagnet is switched OFF to set the object back down again

12. Sorting Scrap Metal
Electromagnets can be used to sort steel food cans from aluminium drinks cans for recycling
The magnets will attract the steel cans
The aluminium in drinks cans is not magnetic – these cans will be left behind

13. HAMMER BELL ELECTROMAGNET Electric Bells
Electric bells need an electromagnet to make them work
BELL
HAMMER
ELECTROMAGNET
The electromagnet pulls the hammer back...
... The electromagnet is then briefly switched off, so...
... It releases the hammer so it falls back and hits the bell

14. What is an electromagnet?
We can make an electromagnet by make a coil of wire with an electrical current in it
A current flowing through a wire produces a weak magnetic field
Magnetic field
If two wires are close enough together their magnetic fields will overlap to make a stronger magnetic field
Current
By coiling our wire, the magnetic fields
from different parts of the wire
will overlap to make a much stronger magnetic field
Current

15. What is the core of an electromagnet?
An electromagnet made from a simple coil of wire is relatively weak
We can increase the strength of the magnetic field by wrapping the coil around a CORE of a magnetic material
Iron makes a good core for an electromagnet – it is easily magnetised when the current is switched on.
When the current is switched off iron loses its magnetism quickly so the magnet stops working immediately
Steel cores are harder to magnetise and then lose their magnetism slowly
Core made from iron nail

16. Making electromagnets stronger
The magnetic field around one coil is quite weak
Increasing the number of coils will make your electromagnet stronger
Moving your coils closer together will make your electromagnet stronger
Increasing the current in the coil will make your electromagnet stronger