Resources:
Plotting magnetic fields - Paper, iron filings, tea strainer, iron nail (or another magnetic object), plotting compasses and two bar magnets.
Magnetic shielding - Paper clip, thread, boss clamp and stand and a selection of magnetic and non magnetic materials.
Handout: Questions related to the mission assignment and space for students to draw their diagrams.
Use the previous lesson to recap learning before beginning the main teaching on magnetic fields.
Ask the students for their ideas on where they see magnets in everyday life and why patterns are created when iron filings are scattered around a magnet.
Answer questions on the first part of the presentation before plotting magnetic field lines using the handout. The students should draw the field lines they see on the illustrations in the handout. Once complete, they can compare and discuss the difference in their magnetic fields. They will then investigate different magnetic materials and magnetic shielding. When completing the magnetic shielding task, they should mark on the handout which materials cause the paperclip to drop and which do not. To stretch themselves, they should think about what materials cause the paperclip to drop, and what they have in common.
Career Film: Take a tour around Rolls Royce SMR's Heritage Museum in Derby to find out about Chris Lancaster's job. Chris works as the Head of IT Portfolio Delivery Lead for Rolls Royce SMR.
Expert Film: This is Chris Lancaster. Chris works as the Head of IT Portfolio Delivery Lead for Rolls Royce SMR. Listen to Chris as he explains the shape of a magnetic field.
Plotting magnetic fields
Students should plot the magnetic field of magnets in three different situations. To do this, they can either use iron filings or plotting compasses. To plot magnetic field lines using iron filings, be sure to place a piece of paper on top of the magnet so the filings do not stick to the magnet. It might also be helpful to place two books on either side of the magnet(s) so the filings have a flat surface to land on.
The three situations are: a single magnet with a magnetic material attached, two magnets attracting (place a wooden block in the middle of the magnets to stop them sticking together), and two magnets repelling.
Magnetic shielding
Students need to set up this investigation by following the steps laid out in the handout. Once they have done this, they can slide different materials between the magnet and the paperclip. It is important that they are given a range of magnetic and non magnetic materials for this investigation to work.
Support Task: Using irons filings first, show the pattern of the magnetic field and discuss the shape as a class. Students can sketch it on a mini whiteboard. Then, when they plot with compasses, they have an idea of what the field lines will look like.
Challenge Task: Not all magnets have the same pattern of field lines. Ask the students to write down how field lines can be different and examples of when these differences would be useful in everyday life.
OR
After the practical, list control variables and how if these were not controlled the practical conclusions may not be valid.
Use a class discussion to ask students to reflect on what they have learned about the shape of magnetic fields, and to share any questions or insights they have gained from the lesson. Reinforce key concepts and address any remaining misconceptions.
Magnets have areas of magnetism called magnetic fields that surround it. These areas are invisible but still observable through the effects that they leave.
There are different ways in which you can 'find' existing magnetic fields and clearly show magnetism. First of all, you may use iron filings. A piece of paper should be placed over a magnet which will initially prevent the iron filings from attaching to the magnet. The filings should then be sprinkled onto the paper before tapping the paper to spread them out. Although we cannot see magnetic fields with the naked eye, we can observe its effects by looking at the ways the iron filings have fallen around the magnet.
To understand this better, you can draw magnet field diagrams. It is important to make sure that every field line leaves from the north pole and enters the south pole, has an arrowhead and is more concentrated at the poles. These lines are also useful in showing us effective magnetic attraction and repelling.
The other method of observation is to use a plotting compass, which detects magnetic fields. During this procedure, a bar magnet is placed at the centre of a piece of paper. The position of both the north pole and south pole are distinguished by making a mark with a pencil on both ends. A compass is placed at one of the poles and then moved across until it reaches the 'mark' of the other pole. The new position is marked with another dot and this process is repeated until a series of dots are joined to give magnetic field lines on both sides of the bar magnet.