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4. "For example, students might learn about Ohm's law, one of
the guiding
principles of physics, which states that electrical current decreases
proportionately as resistance increases in an electrical
circuit operating
under a condition of constant voltage.
In practice, the
principle accounts
for why a flash-light with corroded electrical contacts does
not give a
bright beam, even with fresh batteries.
It is a simple relationship,
expressed as V=IR, and embodied in high school Physics
Standard 5.b.
In a
laboratory exercise, however, students may obtain results that seem to
disprove the linear relationship because the resistance of a
circuit element
varies with temperature.
The temperature of the components gradually
increases as repeated tests are performed, and the data become skewed.
In the foregoing example, it was not Ohm's law that was wrong but an
assumption about the stability of the experimental apparatus.
This
assumption can be proven by additional experimentation and provides an
extraordinary opportunity for students to learn about the
scientific method.
Had the students been left to uncover on their own the
relationship between
current and resistance, their skewed data would not have
easily led them to
discover Ohm's law.
A sensible balance of direct instruction and
investigation and a focus on demonstration of scientific
principles provide
the best science lesson."