Tell the person next to you… 1. If the field lines are close together, what does this tell you about the field? 2. If the field lines are widely spaced, what does this tell you about the field? 3. If the magnetic field lines are parallel to each other, what does this tell you about the field?
Answers 1. The field is strong 2. The field is weak 3. The field is of a constant strength - a "uniform" field
6.7
28 November 2011
15:08 · 6.7 know how to use two permanent magnets to produce a uniform magnetic field pattern
· When the field lines are parallel, the field will be uniform
Observing the magnetic field around a bar magnet and a wire
magnetic field around a bar magnet and wire
· Use iron filings to observe the magnetic field around a bar magnet · Use plotting compasses to observe the field · Use the 3D field demonstrator to observe field
18:23 · Magnetic materials are attracted by magnets. · Can you list the 5 magnetic materials?
(3 elements, 2 compounds)
Answer
3 elements 1. Fe (iron) 2. Co (cobalt) 3. Ni (nickel)
2 compounds 1. Steel (an alloy of iron) 2. Fe3O4 (magnetite (lodestone), one of the oxides of iron)
And the exceptions that prove the rule… ? · Magnet moves water - diamagnetism
· Levitating frog...
· Ferrofluids…
(Picture on page "6.4 6.5 6.6 6")
6.2
01 December 2011
18:21 · 6.2 recall that magnets repel and attract other magnets, and attract magnetic substances
Question
You have 3 bars that all look the exactly the same but they are made from: 1. a magnet 2. steel 3. aluminium
You are given a horseshoe magnet. How can you use this to tell which bar is which?
Answer 1. The bar magnet will be attracted to one pole of the horseshoe magnet and repelled by the other 2. The steel bar will be attracted to both poles of the horseshoe magnet 3. The aluminium bar will be attracted to neither pole of the horseshoe magnet
15:07 · 6.5 understand that magnetism is induced in some materials when they are placed in a magnetic field · 6.3 recall the properties of magnetically hard and soft materials
Practical 1. Stroke a magnet along a steel bar and an iron bar 2. Try picking up some bar clips 3. Bang both bars on the desk 4. Now try picking up the paperclips again 5. Repeat the experiment but this time put the bars inside an electromagnet instead of stroking them
Explanation · Steel is a magnetically hard material. It retains its magnetism when magnetised · Iron is a magnetically soft material. It can be magnetised, but easily loses its magnetism
Model 3 · What do the "smoke" particles look like? · Why are they moving? · What do the "air" particles look like?
5.11 explained
Model 1 · What does the red puck represent? o The large, visible smoke particle · What do the metal balls represent? o The small, not visible air particles
Model 2 · What do the small red particles represent? o The small, not visible air particles · What does the large blue particle represent? o The large, visible smoke particle · What does the view on the left of the screen represent? o The view through the microscope lense · Why can‘t you see the red particles in this view? o They are too small to see
Model 3 · What do the "smoke" particles look like? o They are the 5 large, sand coloured particles · Why are they moving? o Small, fast moving air particles are colliding with the smoke particles and making them move · What do the "air" particles look like? o They are the numerous, small, white particles
5.11 Questions
1. Draw the path of a smoke particle in air (3 marks) 2. Explain what is meant by Brownian Motion of smoke particles in air and how it provides evidence for air particles (4 marks) 3. What change would you expect to see in the movement of the smoke particles if the air was cooled down? Why? (2 marks)
Questions · Why does the needle on the meter move when gas particles are introduced into the box? · What does the meter measure?
Answers · The gas particles collide with all of the walls of the container. The wall on the right moves outwards and moves the needle. · Pressure. The gas particles colliding with the walls makes a force on the walls. The walls have a surface area so the quantity measured is pressure, p=F/A.
5.12+5.15 Questions
02 November 2011
15:55 · 5.12 recall that molecules in a gas have a random motion and that they exert a force and hence a pressure on the walls of the container · 5.15 understand that an increase in temperature results in an increase in the speed of gas molecules [cid:image001.png@01CC9986.E18EA0B0]
Try the animation http://www.lon-capa.org/~mmp/kap10/cd283.htm 1. How do the particles create a pressure? 2. If you increase the temperature, how does the movement of the particles change? 3. If you increase the temperature, how does the number of collisions per second change? 4. If you increase the temperature, what does this do to the pressure?
Tell the person next to you… · How do particles in move in a solid, a liquid and a gas? · Describe… o speed of particles o relative position of particles (fixed or not) o pattern of particles (regularly arranged or not) o size of the particles o space between the particles o strength of bonds between the particles
· 5.7 understand that a substance can change state from solid to liquid by the process of melting · 5.8 understand that a substance can change state from liquid to gas by the process of evaporation or boiling
· The bottom hole squirts water the furthest · Because the water at the bottom has the greatest pressure · Because in the formula ∆p = h × ρ × g, ρ is constant, g is constant and h is large · So ∆p = large
· Your finger pushes on the pin and the pin pushes back on your finger · N3L tells us that all these two forces are equal in size · The pin pushes on the wall and the wall pushes back on the pin · N3L tells us that all these two forces are also equal in size · If the surface area is large then the force is spread over a large area and the pressure is low · If the surface area is small then the force is spread over a small area and the pressure is high · You would like the pressure on your finger to be low and the pressure on the wall to be high · The other way round is painful!
5.4
07 October 2011
10:37 · 5.4 recall and use the relationship between pressure, force and area:
