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 time and the rise in temperature Δθ was recorded. This was repeated for different values of I. The table shows the data recorded. (i) Draw a labelled diagram of the apparatus used. (ii) How was the current changed during the experiment? (iii) Copy the table and complete it in your answerbook. (iv) Using the data in the completed table, draw a graph on graph paper of Δθ against 1/I². Put I² on the horizontal axis (X-axis). (v) Explain how your graph verifies Joule's law (Δθ ∝ I²).

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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.

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Answer

To draw a labelled diagram of the apparatus, include the following components:

Power Supply: A device that provides electrical energy.
Heating Coil: The coil where the current flows, causing the water to heat.
Calorimeter: The insulated container where the water is held.
Ammeter: To measure the current flowing through the circuit.
Thermometer: To measure the rise in temperature of the water.
Variable Resistor: To adjust the current flowing through the circuit.
Insulation: To minimize heat loss to the environment.

Ensure all components are properly connected in a closed circuit.

Step 2

How was the current changed during the experiment?

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The current was adjusted by modifying the variable resistor or changing the power supply settings. This allowed for the generation of different current values (I) to observe the corresponding temperature changes in the water.

Step 3

Copy the table and complete it in your answerbook.

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Answer

Here is the completed table:

1/I (A)	1/I² (A²)	Δθ/°C
1.0	1.0	2.2
1.5	0.444	4.8
2.0	0.25	6.8
2.5	0.16	8.8
3.0	0.111	12.0
3.5	0.081	16.0
4.0	0.0625	20.0

Step 4

Using the data in the completed table, draw a graph on graph paper of Δθ against 1/I².

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Answer

To graph Δθ against 1/I²:

Label Axes: The horizontal axis (X-axis) should be labeled as 1/I² and the vertical axis (Y-axis) should be labeled as Δθ.
Plot Points: Plot each data point based on 1/I² and its corresponding Δθ.
Draw Line: Connect the points with a straight line or curve to reflect the relationship. The line should ideally pass through the origin, showing a direct proportionality between Δθ and 1/I².

Step 5

Explain how your graph verifies Joule's law (Δθ ∝ I²).

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Answer

The graph verifies Joule's law because it shows a linear relationship between Δθ and 1/I². A straight line through the origin indicates that as the current increases, the temperature rise (Δθ) increases with the square of the current. This can be interpreted as Δθ ∝ I², confirming that the increase in temperature is proportional to the square of the electrical current.

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

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

Draw a labelled diagram of the apparatus used.

How was the current changed during the experiment?

Copy the table and complete it in your answerbook.

Using the data in the completed table, draw a graph on graph paper of Δθ against 1/I².

Explain how your graph verifies Joule's law (Δθ ∝ I²).

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