In an experiment to verify Joule's law, a constant current, I, was passed through a heating coil immersed in water. The current was allowed to flow for 3 minutes and the final temperature θ of the water was then measured. This was repeated for a number of different currents. In each case, the initial temperature of the water was 18 °C and the mass of the water was 90 g. The following data were recorded. I (A) 1.5 2.0 2.5 3.0 3.5 4.5 5.5 θ(°C) 20.0 22.0 24.0 27.5 30.5 38.0 49.5 Draw a diagram of the apparatus used in this experiment. Draw a suitable graph to verify Joule's law. Calculate the slope of the graph and hence calculate the resistance of the heating coil. (specific heat capacity of water = 4180 J kg⁻¹ K⁻¹)

Photo AI

In an experiment to verify Joule's law, a constant current, I, was passed through a heating coil immersed in water - Leaving Cert Physics - Question 4 - 2018

Question 4

In an experiment to verify Joule's law, a constant current, I, was passed through a heating coil immersed in water. The current was allowed to flow for 3 minutes and... show full transcript

Worked Solution & Example Answer:In an experiment to verify Joule's law, a constant current, I, was passed through a heating coil immersed in water - Leaving Cert Physics - Question 4 - 2018

Step 1

Draw a diagram of the apparatus used in this experiment.

96%

114 rated

Answer

To illustrate the apparatus for the experiment verifying Joule's law, draw the following components:

A power supply (represented as a battery).
A variable resistor (to adjust the current).
An ammeter (to measure the current in series).
A heating coil immersed in a beaker or container with water.
A thermometer to monitor the water temperature.

Label each component clearly for clarity and completeness.

Step 2

Draw a suitable graph to verify Joule's law.

99%

104 rated

Answer

To construct a graph for verifying Joule's law, plot the following:

Labelled axes:
- X-axis: Current squared (I²) values with appropriate scaling.
- Y-axis: Change in temperature (Δθ) in °C.
Points plotted:
- Calculate I² for each I value:
  - For I = 1.5 A, I² = 2.25
  - For I = 2.0 A, I² = 4.00
  - For I = 2.5 A, I² = 6.25
  - For I = 3.0 A, I² = 9.00
  - For I = 3.5 A, I² = 12.25
  - For I = 4.5 A, I² = 20.25
  - For I = 5.5 A, I² = 30.25
- Corresponding Δθ values recorded from the table.
Use a straight line with good fit through the origin to connect the points plotted.

Step 3

Calculate the slope of the graph and hence calculate the resistance of the heating coil.

96%

101 rated

Answer

To find the slope of the graph, use the formula:

$\text{slope} = \frac{y_2 - y_1}{x_2 - x_1}$

Selecting points from the graph (for example, (2.0, 4.0) and (4.5, 20.25)):

$\text{slope} = \frac{20.25 - 4.0}{4.5 - 2.0} = \frac{16.25}{2.5} = 6.50$

Using the slope to calculate the resistance (R) of the heating coil, and applying Joule’s law:

$R = \frac{R T}{m c}$ where R = slope,

From the data:

$R = 6.50$
$m = 0.09 kg$ (90 g), $c = 4180 J/kg/K$

This gives:

$R = \frac{6.50}{0.09 \times 4180} \approx 2.06 \Omega$

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

In an experiment to verify Joule's law, a constant current, I, was passed through a heating coil immersed in water - Leaving Cert Physics - Question 4 - 2018

Worked Solution & Example Answer:In an experiment to verify Joule's law, a constant current, I, was passed through a heating coil immersed in water - Leaving Cert Physics - Question 4 - 2018

Draw a diagram of the apparatus used in this experiment.

Draw a suitable graph to verify Joule's law.

Calculate the slope of the graph and hence calculate the resistance of the heating coil.

Join the Leaving Cert students using SimpleStudy...

Other Leaving Cert Physics topics to explore