Batteries, Resistance and Current

762 Words May 13th, 2016 4 Pages
PHYS 1112/2212 spring 2016
LAB #9
Batteries, Resistance and Current
Introduction: Voltage can be thought of as the pressure pushing charges along a conductor, while the electrical resistance of a conductor is a measure of how difficult it is to push the charges along. Using the flow analogy, electrical resistance is similar to friction. For water flowing through a pipe, a long narrow pipe provides more resistance to the flow than does a short fat pipe. The same applies for flowing currents: long thin wires provide more resistance than do short thick wires. The resistance (R) of a material depends on its length, cross-sectional area, and the resistivity (the Greek letter rho), a number that depends on the material. The resistivity
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What is the difference between resistivity (ρ) and resistance (R)? What are the units of each?

Lab Activity: Log on and go to the PhET website (PhET.colorado.edu) Go to simulations, then “electricity” then to the following:

“Battery-Resistor” available at: https://phet.colorado.edu/en/simulation/battery-resistor-circuit Check “show battery” and “show cores”, watch what happens, adjust some variables

1. Why do electrons (blue dots) move? Draw a diagram of the battery, label the flow of electrons. The flow of current (+) is opposite; draw this and note if toward or away from + terminal of the battery.

2. What does the Ammeter (on the left) measure? How is this shown in the simulation?

3. What role do the “green dots” in the resistor play in the simulation? What do you think they represent? What does this tell you about the effect of resistors in a circuit?

4. Increase the resistance (# green dots). What affect does this have on temperature? WHY?

5. When the circuit gets hotter, what affect does this have on current? Explain using kinetic-molecular theory.

6. To make the circuit “cold”, what do you need to do? WHY?

7. Describe the relationship between voltage and temperature.

“Resistance in a Wire” available at: https://phet.colorado.edu/en/simulation/resistance-in-a-wire 1. In this simulation, what variables are you seeing the relationship of. Write the

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