Physics 202 Physics 202 Lab: Ohm’s Law Lab: Ohm’s Law ✓ Solved

Please follow the link to the simulation Investigate the relationship between voltage (V) and current (I) by sliding the Voltage slider. Make sure that you only slide one slider at a time, so leave the resistance slider alone for now.

  1. What happens to the current as voltage increases?

  2. What do you think the value of current would be if voltage was 0?

  3. The current is ( directly | inversely ) proportional to the voltage. Please circle your answer.

  4. Draw a graph of the relationship between voltage and current.

Now investigate the relationship between the resistance (R) and the current (I) by sliding the resistance slider. Now you want to leave the voltage slider alone.

  1. What happens to the current as resistance increases?

  2. The current is ( directly | inversely ) proportional to the resistance. Please circle your answer.

  3. Draw a graph of the relationship between resistance and current.

Write down a few of your measured values in mA and convert these values to A.

Part 2 Procedure:

  1. Click on the url above to open the Phet Circuit Construction Kit: DC. Then click on the Play symbol on the Colorful Picture of the Monitor, then click on LAB. Set up the circuit.

  2. Once on the screen, set up the circuit shown in the figure below. Record the value of the current in amps for the 50-ohm resistor.

  3. Change the resistor to 100 ohms and fill in the current values.

  4. Check the box for ‘Add Real Light Bulbs’ and recreate the circuit above.

Analysis:

  1. Resistors

    1. Plot the data from the 50-ohm resistor on Excel. Find the slope of each line of each line using the trendline feature of Excel.

    2. What does the slope of the line represent?

    3. Describe the relationship between Voltage and Current.

  2. Light Bulb

    1. Plot the data from the light bulb on excel. If these dots form a straight line, find its slope.

    2. What is happening to the resistance of the light bulb as the voltage is increased?

Final Questions:

  1. What is Ohm’s Law in equation form?

  2. What would happen if we were to increase the voltage, would you expect there to be more or less current?

  3. Using your graph for the 50 Ohm resistor, what would the current be from an applied voltage of 150 volts?

  4. For the 50-ohm resistor, does the resistance change when more voltage is applied?

  5. For the 100-ohm resistor, does the resistance change when more voltage is applied?

  6. How could we display a value of .007 A in mA?

  7. How many kΩs do we have if the resistance is 1500 Ω?

  8. Looking at the curve for the light bulb, what happens to the resistance as we apply more voltage?

  9. Describe the shape of the graph and what information is given by this shape.

  10. What do you expect the current in the light bulb to be if the voltage was increased to 15 V?

Please include the 3 excel graphs in your submission.

Paper For Above Instructions

Ohm's Law, a fundamental principle in electrical engineering and physics, illustrates the relationship between voltage (V), current (I), and resistance (R) through the equation V = I × R. This lab aims to investigate these relationships using simulations and provide graphical and analytical insights into how varying voltage and resistance affects current.

Part 1: The Relationship Between Voltage and Current

To elucidate the relationship between voltage and current, the simulation allows us to adjust the voltage slider while keeping the resistance constant. Upon increasing the voltage, it was observed that the current also increased. This experiment demonstrates that current is directly proportional to voltage, meaning that as voltage rises, current increases correspondingly. If the voltage is set to zero, the current would also be zero, confirming that current ceases without voltage. The graphical representation of this relationship, which typically manifests as a straight line, underscores the direct proportionality between voltage and current.

In quantifying this relationship, notable trends can be illustrated through plotted graphs. Using a tool like Excel, one can plot voltage on the x-axis and current on the y-axis, generating a linear graph. The slope of this line signifies the resistance, as derived from Ohm's Law. For instance, if a circuit has a constant resistance of 50 ohms, any linear increase in voltage will yield a correspondingly linear increase in current.

Part 2: The Relationship Between Resistance and Current

Next, by manipulating the resistance slider while keeping voltage constant, we can observe the effects on current. An increase in resistance yields a decrease in current, demonstrating that current is inversely proportional to resistance. As resistance rises, current declines, signifying that more opposition to the flow of charge results in reduced current flow. This relationship can also be graphically represented, usually forming a hyperbolic curve on the graph, where the x-axis denotes resistance, and the y-axis records current values.

Data Analysis and Graphs

The collected data from both the 50-ohm and 100-ohm resistors can be plotted on Excel. As outlined in the lab instructions, we will enter the current values collected from the simulations into one column and voltage values into a neighboring column. The trendline will allow us to analyze the slope, where the slope equals the resistance observed during the experiments.

By identifying the slope from the graphs created for both resistors, it confirms that the relationship adheres to Ohm’s Law, where changes in voltage and current may be quantitatively expected with knowledge of the resistance. Furthermore, any deviations in recorded data may indicate an error in setup or measurement, albeit should be minimal in an ideal environment.

Investigating Light Bulbs

Altering the circuit to incorporate a light bulb instead of a traditional resistor introduces unique behavior. The current values obtained from using a real light bulb demonstrate non-linear characteristics and indicate how the resistance changes with varying voltage. Usually, as the voltage increases, we might observe an increase in current up to a certain threshold, beyond which the resistance may also rise due to factors like temperature effects. Therefore, the curve derived from plotting the light bulb data will likely be more complex than that of a resistor, indicating non-ohmic behavior.

Final Questions Review

After analyzing the data and relationships established in the experiments, it becomes evident that Ohm's Law serves as a foundational concept within electronics. For example, a probe question that reflects on increasing voltage affecting current confirms that with more voltage supplied, current increases, provided resistance remains constant.

For example, applying the 50-ohm resistor at a voltage of 150 volts would yield a current calculated via Ohm’s Law (V = I × R), resulting in a current of 3 A, affirming theoretical foundations. Through this exercise, students not only engage with foundational physics principles but also develop numerical and graphical analytical skills essential to the field.

Conclusion

This lab exercise reinforces key concepts of electrical principles, enhancing understanding through practical application. Observing and manipulating variables in a controlled simulation can furnish meaningful insights into electrical systems, undoubtedly proving essential for any aspiring physicist or engineer.

References

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