NFPA Committe discussion

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Follows are excerpts from the NFPA 70E working groups presentation:


Audience Characteristics Regarding Physics Concepts, (Knight, 2004
in press)
• Based on graduated high school students survey done in 1980-90s.
• Students enter training not as “blank slates” or tabula rasa, but filled with may prior concepts.
– Misconceptions
– Preconceptions
– Alternative conceptions
– Common-sense conceptions
• Students’ prior concepts are remarkably resistant to change.
– Conventional instruction – lecture classes, homework, and exams…--make almost no change in a student’s conceptual beliefs.

Students’ knowledge is not organized in any coherent framework.
– Knowledge of physics consists of discrete facts and formulas only loosely connected to each other.
– The large majority of students have essentially no familiarity with the basic phenomena of electricity or magnetism.
• Experience is limited to changing batteries, turning on switches, or using refrigerator magnets
• Many students believe that insulators can not be charged
• Students do not distinguish between object (insulaltor/conductor) and charge state (charged/neutral)
• Students do not distinguish between charge and current
• Students think “neutral” is a third type of charge.
• Students’ knowledge is not organized in any coherent framework.
• Students reason locally, not globally. In most circumstances, they do not see that changing one circuit component will affect the voltage and current at other points in the circuit.
• Students have no micro/macro understanding of circuits. They do not see any connection between macroscopic quantities, such as current or resistance, and their previous understanding of charges, forces, and fields.

• Research by Halloun and Hestenes, 1985
– Students found to hold firm in mistaken beliefs even when shown a demonstration that directly contradicted their predictions.
– Rather than question their own beliefs, the students tried to argue that the demonstration was not relevant to the question they had been asked.
– Results of study: Students’ alternative conceptions are little changed by conventional instruction.

Most common student beliefs about electrical circuits:
– Current is “used up” as it moves through a circuit
– A battery is a source of constant and unchanging current
– Current divides equally when it reaches a junction
– Concept of electricity is used vaguely, interchangeably, with either current or energy.
 
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