Magnetism

1. A student’s understanding and misconceptions Magnetism

2. What is magnetism? • Some definitions… • The class of phenomena exhibited by a magnetic field. • The force exerted by a magnet. • Unusual power to attract, fascinate, or influence. • Magnetism is a force of attraction or repulsion caused by moving electrically charged particles or is inherent in magnetic objects such as a magnet.

3. Misconceptions • Difficult to define and understand because forces are “unseen.” • Many students associate magnetism with gravity. • “Gravity is a magnetic force pulling objects towards the Earth.” • “Magnetism is a type of gravity.”

4. Misconceptions • People are sometimes referred to as having a magnetic personality. They attract others. This use may contribute to some misunderstandings. • Often think that big magnets are stronger than small ones. (Stored power) • All metals are magnetic or can be affected by the forces of magnetism. (Cu, Al) • Some thought that “chemicals made them stick.”

5. Almost all are familiar with magnets and the actions of magnets. • Most were familiar with attraction and not so familiar with repulsion. • 25% responded accurately when tested on attraction and repulsion.

6. Magnetic Attraction

7. Magnetic Repulsion

8. Many misconceptions about the poles of magnets. • Representation of a cut magnet. • Always have two poles.

9. Approaches which draw in everyday experience and focus upon the uses of magnets are beneficial to students. • Important details are often left out.

10. Sound

11. Misconceptions • Again, difficult to understand because sound cannot be seen. • One of the basic senses. Before we are even born we begin to perceive sound. • In the case of some instruments, students thought that sound was inside the instrument and only “released” by human action.

12. Misconceptions • No perception of the sound “traveling.” • Most had no idea that a medium, like air, is needed for sound transmission.

13. Most believe that sound comes from the object, with no perception of what is happening to the air, or medium. • The old philosophical riddle

14. More advanced students might define sound as the detection of vibration and not the production of those vibrations. • Different productions of sound gave different results. • Objects which could be seen vibrating, like a guitar string and cymbal. • More students could understand that the vibrations were being transferred to the air as sound waves. • Objects like rocks were thrown against each other. • Students gave reference to the properties of the stones.

15. A Definition • Mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium (as air) and is the objective cause of hearing.

16. Heating

17. Misconceptions • Students think of heat as a ‘substance.’ • Thought of as being able to flow in and out of objects. • Often associated with air temperature. • Heat and cold thought of as opposites instead of being part of the same continuum.

18. Misconceptions • Heat is only associated with very hot things or large amounts of heat. • Human body temperature is the standard for measuring heat. • Manufactured heat is a different form from natural heat. • Some objects are naturally warmer or colder than others

19. Misconceptions • Students understand that… • Heat rises • Hot things expand • Heat travels through metals • These things are often known through observations but are never explained as to why they occur. • Distinguishing between heat and temperature is difficult. (ages 10-16)

20. Heating is the movement of energy. • Heat is the amount of thermal energy that is transferred between two objects due to a temperature difference.