N S Slide 2 If you sprinkle iron filings around a bar magnet you can see a pattern form. What is this pattern? What do the arrows on the lines show? What does it tell you about the strength of the magnetic field where the lines are: Close together? Far apart? Mark on the diagram the points where the field is the weakest. What causes the steel bar to have a magnetic field? E J Vine.

Magnetism is caused by the movement of positive or negative charges. An Atom Atoms have electrically charged particles inside. The positive particles called PROTONS ATTRACT the negative ones called ELECTRONS This force of attraction keeps the electron in orbits around the centre of the atom called the NUCLEUS. + Magnetism is caused by the movement of positive or negative charges. Moving Negative electrons in atoms give substances magnetic properties. Look at the picture which shows the inside of an atom. Name the main particles which are found in atoms and write down what charge each carries. Particle name ……………………… Charge it carries…………….. Electrons are negatively charged. PROTONS are positively charged. What charge do the neutrons have?............... The cluster of particles in the middle of the atom are held together with very strong forces, this cluster is called the NUCLEUS of the atom. The opposite charges attract each other and this is what keeps the electrons orbiting the nucleus of the atom. What stops the electrons just flying off and escaping from the atom?.................................................................................................................................................... Neutrons have no electrical charge Magnetism is caused by the movement of positive or negative charges. Moving Negative electrons in atoms give substances magnetic properties... E J Vine.

Magnetism is caused by the movement of positive or negative charges. An Atom Atoms have electrically charged particles inside. The positive particles called PROTONS ATTRACT the negative ones called ELECTRONS This force of attraction keeps the electron in orbits around the centre of the atom called the NUCLEUS. + Orbiting electrons produce tiny magnetic fields. Any positive or negative particle when moving produces a tiny magnetic field. Which metal produces the strongest magnetic field when magnetised? (hint. It is used to make magnets) ……………………………………………………………. Neutrons have no electrical charge Magnetism is caused by the movement of positive or negative charges. Moving Negative electrons in atoms give substances magnetic properties... E J Vine.

Atomic magnets North South Electrons ‘circling’ in atoms make the atoms behave like tiny magnets: This effect is very strong in iron If you could see these tiny atomic magnets you would see that they form magnetic groups called domains. Iron is the element which produces the strongest magnetic fields If you could see these tiny atomic magnets you would see that they form magnetic groups called domains. The domains can be lined up inside an iron or steel bar. All you need is a magnetic field to line them up.

An iron or steel bar which has not been magnetised. No magnetic force field The atomic magnets point at each other N to S and S to N. When they are like this then the magnetic fields effectively cancel and the bar has no external magnetic field. Atomic Magnets all jumbled pointing at each other: Their fields cancel each other and this iron or steel bar would not be magnetic

Unmagentised steel or iron bar The field from the red permanent magnets will gradually line up the magnetic domains. E J Vine.

The magnetic force field from the permanent magnets line up the atomic magnets and will make the steel or iron bar magnetic. N S The field from the red permanent magnets gradually line up the magnetic domains. E J Vine.

The magnetic force field from the permanent magnets lines up the atomic magnets and will make the steel or iron bar magnetic. N S The field from the red permanent magnets gradually line up the magnetic domains. E J Vine.

The magnetic force field from the permanent magnets lines up the atomic magnets and will make the steel or iron bar magnetic. N S The field from the red permanent magnets gradually line up the magnetic domains. E J Vine.

The magnetic force field from the permanent magnets lines up the atomic magnets and will make the steel or iron bar magnetic. N S The field from the red permanent magnets gradually line up the magnetic domains. E J Vine.

The magnetic force field from the permanent magnets lines up the atomic magnets and will make the steel or iron bar magnetic. N S S N The blue bar now produces its own magnetic field. E J Vine.

S The blue magnet now has its own magnetic field N The field from the red permanent magnets has lined up the domains and the blue bar has now become magnetic. E J Vine.

S N N S Complete the following sentence: TEMPORARY MAGNETS ARE MADE OF IRON : When the domains are lined up the bar becomes magnetic. The domains in pure iron are easily lined up, iron is easy to magnetise. However, even the warmth of the room gives the domains enough energy to jumble up again and the bar easily looses its magnetic field. N S S N TEMPORARY MAGNETS ARE MADE OF IRON : When the domains are lined up the bar becomes magnetic. The domains in pure iron are easily lined up, iron is easy to magnetise. However, even the warmth of the room gives the domains enough energy to jumble up again and the bar easily looses its magnetic field. The bar becomes magnetic and it produces its own magnetic field. Complete the following sentence: Temporary magnets are made of pure………………………. Temporary magnets are easy to ………………………………….. And easy to de…………………………………… List TWO WAYS that a temporary magnet may be demagnetised. …………………………………………………………………………………………………………………….. E J Vine.

Heat from the room is sufficient to give the domains energy, this destroys the orderly lines, the magnetic field will disappear. S N Heat from the room is sufficient to give the domains energy, this destroys the orderly lines, just like a line of pupils will fall part when left!!!!!!! heat E J Vine.

heat The magnetic force field gradually disappears. N The field gradually……………………………………… heat E J Vine.

No field left!!!! E J Vine.

Permanent MAGNETS ARE MADE OF Steel plus impurity atoms like Al aluminium, Ni nickel, Co cobalt They are called AlNiCo Magnets N S S N Al The impurity atoms make it difficult to magnetise Al Ni Co magnets but they also lock the domains in position once they are lined up. This makes them into good material for Permanent magnets. What is it about permanent magnets that makes them different from temporary magnets:…………………………………………………………………… Why is it difficult to demagnetise permanent magnets? ………………………………….. And difficult to de…………………………………… Explain TWO WAYS that a permanent magnet may be magnetised. …………………………………………………………………………………………………………………….. Ni The impurity atoms make it difficult to magnetise Al Ni Co magnets but they also lock the domains in position once they are lined up. Co E J Vine.

Permanent MAGNETS ARE MADE OF Steel plus impurity atoms like Al aluminium, Ni nickel, Co cobalt They are called AlNiCo Magnets N S S N Al The impurity atoms make it difficult to magnetise Al Ni Co magnets but they also lock the domains in position once they are lined up. This makes them into good material for Permanent magnets. What is it about permanent magnets that makes them different from temporary magnets:…………………………………………………………………… Why is it difficult to demagnetise permanent magnets? ………………………………….. And difficult to de…………………………………… Explain TWO WAYS that a permanent magnet may be magnetised. …………………………………………………………………………………………………………………….. Ni heat Co E J Vine.