In this experiment, students will use a current and voltage sensor to discover the relationship between the voltage and current in a DC circuit.

• PASPORT
• 500 Interface
• 750 Interface

1. Make sure you have good connections at each junction in the circuit.
2. Place one D cell in the battery holder; the bulb should light. If not, troubleshoot your circuit for a complete conducting path.
3. Click Start and note the readings on the voltage and current digits displays.
4. Record the voltage and current in the data table.
5. Repeat steps 2-3 with two, three and four batteries in the holder. You should have a total of four data runs.
6. Replace the long bulb in socket with the 10 ohm resistor. Repeat steps 2-5 with the resistor.
   

• DataStudio

1. What relationship exists between current and voltage for the light bulb?
2. What relationship exists between current and voltage for the resistor?
3. Why is the voltage-current relationship different for a light bulb vs. a resistor?
4. What specific equation describes this relationship for the resistor? (Include numbers and units for both the slope and vertical intercept)
5. What is the physical meaning of the slope for the voltage-current graph (resistor)?
6. What is the physical meaning of the vertical intercept for the voltage-current graph (resistor)?
7. Scientists call the slope of the voltage-current graph resistance of the circuit. Why do you think this name was give to the slope of the voltage-current graph?
8. Rewrite your equation from question #4, but this time substitute the variable R (resistance) for the slope. This is the mathematical representation of Ohm's law.
9. Optional – Repeat the data analysis, this time using a 20 ohm resistor instead of the 10 ohm resistor. How does the slope of the voltage-current graph change, when this resistor is used? How does the circuit behave differently with the 20 ohm resistor in the circuit?