Cosmic Rays. Cosmic rays are very high energy particles. Most cosmic rays come from outer space, outside our solar system

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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 Explosions inside the Sun produce cosmic rays - 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 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 Electrical currents in the Earth s molten iron outer core produce a magnetic field 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

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: o The CORE this is a piece of iron or a permanent magnet o The COIL o 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 Electric Bells Electric bells need an electromagnet to make them work HAMMER BELL 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 Magnetic field 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 Current If two wires are close enough together their magnetic fields will overlap to make a stronger magnetic field By coiling our wire, the magnetic fields from different parts of the wire will overlap to make a much stronger magnetic field Current

15 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 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 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