11/12 / 13 Intro to magnetism

1. 11/12/13Intro to magnetism • Science podcast: Antarctic Adventures • Talk about Power, do the light bulb math • Work on switch designs • Discuss Combination circuit worksheet • Introduction to magnets • Hand in your notebook • Homework: If you haven’t done so already, read the Magnet handout on the course website and here.

2. Learning objectives • Sketch the orientation and direction of magnetic field lines of a bar magnet and of the Earth. • Describe how a compass works. Why is one end painted? What does the painted end point to?

3. Rate the bulbs from brightest to dimmest 1. Predict 2. Test 3. Show with math A D B E C F

4. Planning your house • Design a plan for a single switch that controls two things with one being on at a time or both off. • Design a plan for an object that’s controlled by two switches such as a living room light that can be turned on and off from the front door or the kitchen. This is called a 3-way or double switch on the assignment sheet. • You should be able to power the object by moving only one switch or the other no matter the position of the 2nd switch. These switches must be apart from each other. • Test these out with your materials and using the PhET circuits simulation found at http://goo.gl/uYiX . • Note: I changed my mind about using the Snap kits. Sorry.

5. 1 switch that controls two things

6. 1 switch that controls two things

7. Simplest double switch (3-way switch)

8. Simplest double switch (3-way switch)

9. Circuit conclusions • Resistance • Ohm’s Law • Power • Series circuit • Always same current through each bulb • Parallel circuit • Always same voltage across each bulb

10. Introduction to magnets – Bag o’ Stuff • Materials: bar magnet, Bag o’ Stuff • Explore the objects in your bag. Which of them are magnets? Magnetic materials? Non-magnetic materials? • Develop a list of characteristics that covers each item in each of the categories above. • Share these characteristics with the class.

11. Magnetic field lines • Magnets affect the space around them. Scientists call the extent of this effect a magnetic field. • The strength of a magnet can be represented by magnetic field lines. • The more line passing through an area, the stronger the field in that area. • All magnets have two poles, a north and a south • Field lines outside a magnet go from north to south

12. Tracing magnetic field lines • Materials: bar magnet, compass • Use the compass to trace at least four magnetic field lines on the outside of your magnet. • Which pole does the red side of the compass point to?

13. Earth as a magnet It turns out that the Earth is a big magnet. (What is the evidence of that?) Where is the south pole of the big magnet we call Earth? The north pole? What is your evidence of that?

14. Earth as a magnet • It turns out that the Earth is a big magnet. (What is the evidence of that?) • Where is the south pole of the big magnet we call Earth? The north pole? What is your evidence of that? • Use your knowledge to determine the poles of an unmarked magnet

15. PhET Electromagnets activity • Explore a bar magnet and electro-magnet • Design an experiment to study magnetism http://goo.gl/tpq32