3 - PS2.B (B) - Electric and Magnetic Forces - FINAL (WND 3/14/14)

Module: Electric and Magnetic Forces

DCI: PS2.B (B) Types of Interactions – Electric and magnetic forces between a pair of objects do not require that the forces between a pair of objects be in contact. The sizes of the forces in each situation depend on the properties of the objects and their distances apart and, for forces between two magnets, on their orientation relative to each other.

PE: 3-PS2-3 Ask questions to determine cause and effect relationships of electric or magnetic interactions between two objects no in contact with each other.

PE: 3-PS2-4 Define a simple design problem that can be solved by applying scientific ideas about magnets.

[Clarification Statement: Examples of an electric force could include the force on hair from an electrically charged balloon and the electrical forces between a charged rod and pieces of paper; examples of a magnetic force could include the force between two permanent magnets, the force between an electromagnet and steel paperclips, and the force exerted by one magnet versus the force exerted by two magnets. Examples of cause and effect relationships could include how the distance between objects affects strength of the force and how the orientation of magnets affects the direction of the magnetic force.] [Assessment Boundary: Assessment is limited to forces produced by objects that can be manipulated by students, and electrical interactions are limited to static electricity.]

Examples of problems could include constructing a latch to keep a door shut and creating a device to keep two moving objects from touching each other.]

The ideas are: 

- electric and magnetic forces between a pair of objects do not require the objects to be in object. 

- the size of the forces in each situation depend on the properties of the objects and their distances apart

- For forces between two magnets, their orientation relative to each other affects the size of the force

For students to 'ask questions', we might have to provide some background on an investigation and ask which question students were likely trying to answer. We can also ask one or two questions about the basic idea that objects can exert forces on each other without being in contact, and which factors affect the size of the force between two objects.