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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 - 2007
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 ti... 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 - 2007
Step 1
Draw a labelled diagram of the apparatus used.
Answer
To create a labelled diagram, include the following components:
- Power supply: Represents the source of electrical energy.
- Heating coil: The element that converts electrical energy into heat.
- Ammeter/multimeter: To measure the current flowing through the circuit.
- Thermometer: Placed in the water to measure the temperature rise.
- Calorimeter: A container holding a fixed mass of water to observe the temperature change.
- Insulation: To minimize heat loss to the surroundings.
- Stop watch: To measure the time during which the current flows.
Make sure to label each component clearly in the diagram.
Step 2
How was the current changed during the experiment?
Answer
The current was changed by adjusting the variable power supply or by varying the resistance in the circuit. This allowed for different values of current (I) to be applied, and each setting was maintained to record the corresponding rise in temperature (Δθ).
Step 3
Step 4
Using the data in the completed table, draw a graph on graph paper of Δθ against 1/I².
Answer
To draw the graph:
- Place Δθ on the Y-axis and 1/I² on the X-axis.
- Mark the data points based on the values from the completed table.
- Connect the points with a straight line, which should ideally pass through the origin, indicating a linear relationship between Δθ and 1/I².
Step 5
Explain how your graph verifies Joule's law (Δθ ∝ I²).
Answer
The straight line through the origin in the graph indicates a direct proportionality, suggesting that as the current squared increases, the temperature rise (Δθ) also increases. This linear relationship confirms Joule's law, which states that the heat produced in a conductor is proportional to the square of the current (Δθ ∝ I²). Thus, the experiment supports the theoretical predictions of Joule's law.