5-MAG-5

Outcomes

• Pupils can build a working speaker
• Pupils can understand some uses for the motor effect

Specification References

• 6.11 understand that there is a force on a charged particle when it moves in a magnetic fieldas long as its motion is not parallel to the field
• 6.12 understand that a force is exerted on a current-carrying wire in a magnetic field, and howthis effect is applied in simple DC electric motors and loudspeakers
• 6.13 use the left hand rule to predict the direction of the resulting force when a wire carries acurrent perpendicular to a magnetic field
• 6.14 describe how the force on a current-carrying conductor in a magnetic field increases with the strength of the field and with the current.

Starter

Start with some more practice of FLH rule as pupils tend to struggle with this. Have a few examples on the board ready as they come in. Vary the orientations of the different parts and possibly throw in an isometric one. Also change symbols for power supply so that pupils can deal with cells or dc supplies.

Main Body of Lesson

Having started the motor effect and seen the speaker the next practical is to build a small simple DC motor. Some pupils struggle with this. Use the example version to show what it should look like. Ensure pupils get a good connection on the ends of the wires and also ensure that the magnets are attracting. Those who make a good motor should try to make it spin faster and then go and help the people who are still struggling.

Pupils need to be able to suggest how to make the motor spin faster. This can be shown with the large demo motor by increasing the current. Changing the magnetic field strength is a little more tricky.

After the practical pupils will need some good notes on FLH rule and some attention should be given to spec point 6.11 as it's not always clearly covered. Pupils may be asked about positive or negative charges moving in a magnetic field and may need to predict movement of them using FLH. This is easy for the positive charge as the second finger points in the direction of the movement. However, a negative charge moving one way produces a conventional current flow in the opposite direction. I.e. an electron moving left produces a current to the right. Pupils also need to know that the force acting is maximum when the field and the current are at right angles and zero when they are parallel.

Plenary

Finish with a few more FLH examples, this time including charged particles.

Homework

Read pg 210-213 and answer the questions on pg 211 and 213

Additional Information

Textbook References

pg 210-213

Safety/Hazards

Pupils need to use the tools with care when building their motors. A skin pinch is easy to do with the wire strippers.