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In an experiment to investigate the variation of the resistance R of a thermistor with its temperature θ, a student measured the resistance of the thermistor at different temperatures - Leaving Cert Physics - Question 4 - 2009
Question 4
In an experiment to investigate the variation of the resistance R of a thermistor with its temperature θ, a student measured the resistance of the thermistor at diff... show full transcript
Worked Solution & Example Answer:In an experiment to investigate the variation of the resistance R of a thermistor with its temperature θ, a student measured the resistance of the thermistor at different temperatures - Leaving Cert Physics - Question 4 - 2009
Step 1
Draw a labelled diagram of the apparatus used in this experiment.
Answer
To properly illustrate the setup of the experiment, the labelled diagram should include:
- A diagram of a water bath, indicating that it is filled with water to control the temperature.
- A thermistor positioned inside the water bath.
- A digital multimeter (ommeter) connected to the thermistor to measure the resistance.
- A thermometer placed in the water bath to monitor the temperature accurately.
- A power source (battery) connected to the thermistor for operational purposes.
Clearly label each component with appropriate names.
Step 2
How did the student measure the resistance of the thermistor?
Answer
The student measured the resistance of the thermistor using a digital multimeter. The multimeter was set to measure resistance (Ω). The student connected the multimeter probes to the thermistor leads, allowing the device to display the resistance value directly on the screen.
Step 3
Plot a graph on graph paper to show the relationship between resistance R of the thermistor and its temperature θ (put θ on the X-axis).
Answer
To plot the graph:
- Label the X-axis as 'Temperature (°C)' and the Y-axis as 'Resistance (Ω)'.
- Mark the points from the data table:
- (20, 2000)
- (30, 1300)
- (40, 800)
- (50, 400)
- (60, 200)
- (70, 90)
- (80, 40)
- Plot these points accurately on the graph paper.
- Connect the points with a smooth curve, as the relationship is expected to be non-linear. The graph should show a decreasing curve, indicating that as the temperature increases, the resistance decreases.
Step 4
Use your graph to estimate the temperature of the thermistor when its resistance is 1000 Ω.
Answer
Referring to the plotted graph, locate the point where the resistance value is approximately 1000 Ω. Follow a horizontal line to intersect the curve, then drop down vertically to read the corresponding temperature on the X-axis. The estimated temperature for a resistance of 1000 Ω falls between 30°C and 40°C, closer to 35°C.
Step 5
What does your graph tell you about the relationship between the resistance of a thermistor and its temperature?
Answer
The graph indicates an inverse relationship between the resistance of the thermistor and its temperature. As the temperature increases, the resistance of the thermistor decreases, suggesting that thermistors are negative temperature coefficient (NTC) devices. This behavior is common in thermistors and highlights their utility in temperature sensing applications.