SCEN103 Class 7
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Resistivity and Play-Doh
Voltmeters and Ammeters
An ammeter measures current through a circuit element;
-- therefore it must be connected in series with it.
An ammeter should have a much lower resistance than the other elements in the circuit;
-- otherwise current may change significantly.
Consider effective resistance.
A voltmeter measures voltage across a circuit element;
-- therefore it must be connected in parallel with it.
A voltmeter should have a much higher resistance than the element in parallel;
-- otherwise voltage will change significantly.
Again, consider effective resistance.
Resistance of a cylinder
From the Play-Doh Page
- Review of circuit used for experiment
- Dependence on length? Demonstration using Play-Doh
- Results: Graph
- Conclusion: Resistance is directly proportional to the length of a cylindrical resistor.
- Dependence on diameter? Group Activity
- Data: collected by groups from previous term
- Graph: R vs. Diameter
- Graph: R vs. Reciprocal Diameter
- Graph: R vs. Reciprocal Area
- Conclusion: Resistance is inversely proportional to the cross-sectional area of a cylindrical resistor.
- The Result!
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Last updated Jan. 9, 1998.
Copyright George Watson, Univ. of Delaware, 1996.