Common Misconceptions
Some of the topics covered in Gravitational, Electric and Magnetic Fields are ideas that student are somewhat familiar with but not fully educated in. The following are some of the common misconceptions that students may have coming into this unit.
1. There is no gravity in outer space.
This misconception can be overcome when learning about Newton's Universal Law of Gravitation. Students will be able to calculate the gravitational field intensity at any given point away from a celestial body and see that there is a force but it is so small that it has almost no affect on an astronaut in outer space. 2. Heavier objects fall faster than lighter objects in a gravitational field This misconception can be overcome when learning about Newton's Universal Law of Gravitation. Students will be able to calculate the gravitational field intensity for any mass a certain distance from a celestial body (such as earth or the moon) and see that the forces may be different but for very light objects (compared to the earth or moon) the force is so small that the difference is negligible. What they see in terms of the delay in falling of a feather is the aerodynamic drag. This misconception will be overcome by showing the following video dropping a feather and a hammer in a vacuum on the moon. 3. There is no gravity on the moon This misconception can be overcome when learning about Newton's Universal Law of Gravitation. Students will be able to calculate the gravitational field intensity at any given point away from the moon and see that there is a force. The Feather & Hammer drop on the moon video will also overcome this misconception by showing that things do fall on the moon, just at a slower rate. |
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4. Electric field lines show the direction charges move.
This misconception can be overcome by showing the students that the field lines show the direction of force that a charge would feel. This is not the direction the charge would move in, but the direction the charge would accelerate in, assuming no other forces exist. Make connection between kinematics and dynamics and a car decelerating but still going forward. The net force is backwards but the car is still moving forwards. 5. All metals are attracted to a magnet This misconception can easily be overcome by showing the students a metal that is not attracted to a magnet such as copper. You can all show that most coins are not magnetic. 6. Only magnets produce magnetic fields This misconception can be overcome by creating a solenoid from a current carrying conductor and placing many compasses inside of the solenoid to show the magnetic field strength from the solenoid. This can also be demonstrated in the videos |