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In an experiment to verify Joule's law, a heating coil was placed in a fixed mass of water - Leaving Cert Physics - Question 4 - 2016
Question 4
In an experiment to verify Joule's law, a heating coil was placed in a fixed mass of water. A current I was allowed to flow through the coil for a fixed length of t... show full transcript
Worked Solution & Example Answer:In an experiment to verify Joule's law, a heating coil was placed in a fixed mass of water - Leaving Cert Physics - Question 4 - 2016
Step 1
Draw a labelled diagram of the arrangement of the apparatus used in this experiment.
Answer
To illustrate the apparatus for verifying Joule's law, the diagram should include:
- A power supply connected to the system.
- A current measuring device (ammeter) in series with the heating coil.
- The heating coil immersed in a calorimeter (or water container).
- A thermometer to measure the temperature of the water.
- An insulating material surrounding the calorimeter to prevent heat loss.
- Show a variable resistor to adjust the current flow.
Label all parts clearly for full marks.
Step 2
How was the current changed during the experiment?
Answer
The current was adjusted by using a variable power supply or variable resistor. By changing the resistance, the flow of current through the heating coil was modified, allowing for different values of I to be tested during the experiment.
Step 3
Step 4
Using the data in the completed table, draw a graph on graph paper of Δθ against I².
Answer
To create the graph:
- Calculate I² for each value of I and plot Δθ against I² on graph paper.
- Use clear axes; label the x-axis as 'I² (A²)' and the y-axis as 'Δθ (°C)'.
- Mark the data points accurately.
- Draw a straight line to connect the points, indicating a proportional relationship, which should ideally be linear.
Step 5
Explain how your graph verifies Joule's law.
Answer
The graph of Δθ against I² should yield a straight line through the origin. This demonstrates that the heat generated (Δθ) is directly proportional to the square of the current (I²), consistent with Joule's law. The relationship confirms that as the current increases, the temperature rise in the water also increases proportionately, validating the principle that the heat produced in a conductor is proportional to the square of the current flowing through it.