Load Resistor in Power Dissipation Experiment

Objective

Understand the relationship between voltage, current, and power dissipation in a load resistor by analyzing how different resistors dissipate power in a simple circuit.

Materials Needed

Theory

Power dissipation in resistors is an important concept in electronics, especially when designing circuits with components that must handle specific power levels. Power (P) dissipated by a resistor is related to the voltage (V) across it and the current (I) flowing through it, as given by:

P = V × I = I2 × R = V2 / R

In this experiment, you will measure how resistors with different values dissipate power when a constant voltage is applied across them. By measuring the current through each resistor and calculating the power dissipation, you can confirm the theoretical relationship.

Steps

  1. Set Up the Circuit

    Place a resistor on the breadboard. Connect the positive terminal of the power supply to one end of the resistor and the negative terminal to the other end. Set the voltage on the power supply to a constant value (e.g., 5V or 12V).

  2. Measure Voltage

    Use a multimeter to measure the voltage across the resistor to ensure that the power supply is providing a steady voltage.

  3. Measure Current

    Use the ammeter (or multimeter in current mode) to measure the current flowing through the resistor. Record the current for each resistor used in the experiment.

  4. Calculate Power Dissipation

    For each resistor, calculate the power dissipation using the measured current and the voltage applied across the resistor. Use the formula P = V × I.

  5. Repeat for Different Resistors

    Replace the resistor with others of different values (e.g., 220Ω, 470Ω, 1kΩ) and repeat the measurements. Compare the power dissipation for each resistor.

  6. Analyze Results

    Plot the power dissipation as a function of resistor value. Notice how lower resistances lead to higher power dissipation, assuming a constant voltage supply. This shows the inverse relationship between resistance and power for a given voltage.

Example Calculation

For a resistor of 220Ω and a supply voltage of 12V, the power dissipation can be calculated as follows:

This value should match the power dissipation measured with the multimeter.

Conclusion

In this experiment, you demonstrated that the power dissipated by a resistor depends on both the voltage applied across it and its resistance. Lower resistance values result in greater power dissipation when voltage is kept constant. This experiment emphasizes the need for careful resistor selection in circuit design, especially when dealing with power-sensitive components.