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 $ heta$ 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 $ heta$ against $1/I^{2}$. Put $I^{2}$ on the horizontal axis (X-axis). (v) Explain how your graph verifies Joule's law ($ heta ext{ against } I^{2}$).

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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 ... 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 illustrate the apparatus used in the experiment, draw a diagram that includes the following components:

Ammeter (for measuring current)
Heating Coil (the main component for heating the water)
Calorimeter (to hold the water)
Thermometer (to measure temperature change)
Variable Resistor (for adjusting the current)
Power Supply (to provide electrical energy)
Insulation (to minimize heat loss)

Ensure all components are properly labeled and the connections are clearly indicated.

Step 2

How was the current changed during the experiment?

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Answer

The current was adjusted by using the variable power supply or by modifying the resistance in the circuit. This allows for incremental changes in the current to study its effect on the temperature rise of the water.

Step 3

Copy the table and complete it in your answerbook.

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Answer

The given data table can be filled out as follows:

$1/I$ (A $^{-1}$ )	$1/I^{2}$ (A $^{-2}$ )	$heta/ ext{C}$
1.0	1.0	2.2
1.5	0.4444	5.8
2.0	0.25	8.8
2.5	0.16	12.6
3.0	0.1111	16.0
3.5	0.0816	20.0
4.0	0.0625	35.2

Step 4

Using the data in the completed table, draw a graph on graph paper of $ heta$ against $1/I^{2}$.

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Plotting Data Points: Using the values from the table, plot the temperature change ( $heta$ ) on the vertical axis against $1/I^{2}$ on the horizontal axis.
Label Axes: Clearly label the axes. Use 'Temperature Change ( $heta/ ext{C}$ )' for the Y-axis and 'Current Inverse Square ( $1/I^{2}$ )' for the X-axis.
Drawing the Graph: Connect the data points with a straight line to reflect the relationship between the two variables.
Checking for Linearity: Ensure the line passes through the origin, confirming the relationship follows Joule’s law.

Step 5

Explain how your graph verifies Joule's law ($ heta ext{ against } I^{2}$).

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Answer

The graph demonstrates that there exists a direct linear relationship between the rise in temperature ( $heta$ ) and the square of the current ( $I^{2}$ ). The straight line indicates that as the current increases, the heat generated in the heating coil also increases proportionally with the square of the current. This is in line with Joule's law, which states that the heat produced in a conductor is proportional to the square of the current flowing through it. Thus, the graph verifies Joule's law effectively.

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 $ heta$ against $1/I^{2}$.

Explain how your graph verifies Joule's law ($ heta ext{ against } I^{2}$).

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