Ohm's Law Lab

What was the name of the first electricity detective? Sherlock Ohms

Objectives: 

• Determine the mathematical relationship between current, potential difference, and resistance in a simple current
• Compare the potential difference vs. current behavior of a resistor to that of a light bulb

Key Terms:

• current
• potential difference
• resistance
• circuit
• voltage
• electric potential

Pre-Lab Discussion: What is Ohm's Law?

Ohm's Law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the following mathematical equation can be used to describe the relationship:

Materials: 

• Vernier Circuit Board
• wires and clips
• two resistors (10 and 50)
• light bulb (6.3 V)
• Vernier Current and Voltage Probe

Lab Setup: 

Procedure:

1. Resistor One (10Ω) - The power supply was connected and data was kept at every 0.5 V

     At event number five, our Current (A) is 0.2063 and our Potential (V) is 2.023. When we divide our voltage by our current, we get a resistance of about 9.806, which is close to the actual resistance of 10 

Ω

2. Resistor Two (50Ω) - The power supply was connected and data was kept at every 0.5 V

    At event number two, our Current (A) is 0.0326 and our Potential (V) is 1.665. When we divide our voltage by our current, we get a resistance of about 51.07, which is close to the actual resistance of 50 

Ω

3. Lightbulb (6.3 V) - The power supply was connected and data was kept at every 0.5 V (versus every 0.1 V) 

   Based upon this data, we can assume that the resistance of the lightbulb is about 36.58 Ω

Analysis:

In this lab, we are trying to prove the relationship of R = V/I, V standing for voltage, I for current, and R or resistance. Graphs one and two, which display potential voltage on the y-axis and current on the x-axis, proves the two are proportional. The slopes of the graphs, which are nearly identical to the resistance of each resistor, prove the proportional relationship between the two. The data of both Graph one and two is in a straight line that passes through zero, proving the proportional relationship between the current and voltage. 

We know that the resistors follow Ohm's Law because the relationship between I, V, and R is followed between two points and the voltage divided by the current is equal to the resistance.

For the section of the lab that involved the lightbulb, the change was linear. Based upon the slope of the graph, we believe the light bulb has a resistance of about 36.58 Ω. As the voltage increased, the current remained with it in a proportional relationship, following Ohm's Law.