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A project was launched to establish the best fixed tilt angle at which solar panels should be installed to give the user the maximum amount of energy output when measured over a period of one year (annual energy output). Energy output refers to the amount of energy in kWh which is converted from sunlight energy to electrical energy and made available to output devices such as electrical appliances.

Seven solar panels were installed in an open field. Each panel was installed at a different fixed tilt angle. The energy output of the seven panels was then measured over a period of exactly one year (365 days).

The RESULTS can be found in the table below:

\begin{tabular}{|c|c|c|}
\hline
Panel Number & \begin{tabular}{c}
Tilt (angle with the \\
horizontal plane)
\end{tabular} & \begin{tabular}{c}
Total annual energy output of the panel \\
(kWh/year)
\end{tabular} \\
\hline
1 & [tex]$0^{\circ}$[/tex] & 350 \\
\hline
2 & [tex]$10^{\circ}$[/tex] & 370 \\
\hline
3 & [tex]$20^{\circ}$[/tex] & 390 \\
\hline
4 & [tex]$30^{\circ}$[/tex] & 410 \\
\hline
5 & [tex]$40^{\circ}$[/tex] & 385 \\
\hline
6 & [tex]$50^{\circ}$[/tex] & 360 \\
\hline
7 & [tex]$90^{\circ}$[/tex] & 220 \\
\hline
\end{tabular}

4.1 Draw a bar graph to illustrate the annual energy output at different tilt angles for the seven solar panels. (6)

4.1.1 Which tilt angle gives the highest annual energy output? (1)

4.2 Which factors were kept constant (which variables were controlled) during this experiment? (3)

4.3 Identify the independent variable in this experiment. (1)



Answer :

GinnyAnswer
Let's break down the solution step-by-step:

### Question 4.1: Draw a bar graph to illustrate the annual energy-output at different tilt angles for the seven solar panels

To illustrate the annual energy output at different tilt angles, we would plot a bar graph where:
- The x-axis represents the tilt angles.
- The y-axis represents the annual energy output (in kWh).

Here are the data points:
- Tilt angle [tex]\( 0^\circ \)[/tex] with 350 kWh/year
- Tilt angle [tex]\( 10^\circ \)[/tex] with 370 kWh/year
- Tilt angle [tex]\( 20^\circ \)[/tex] with 390 kWh/year
- Tilt angle [tex]\( 30^\circ \)[/tex] with 410 kWh/year
- Tilt angle [tex]\( 40^\circ \)[/tex] with 385 kWh/year
- Tilt angle [tex]\( 50^\circ \)[/tex] with 360 kWh/year
- Tilt angle [tex]\( 90^\circ \)[/tex] with 220 kWh/year

A sample bar graph can be drawn using this data.

### Question 4.1.1: Which tilt angle gives the highest annual energy-output?

To determine which tilt angle yields the highest annual energy-output:
- From the data, examine all the annual energy outputs:
- [tex]\(0^\circ\)[/tex] → 350 kWh
- [tex]\(10^\circ\)[/tex] → 370 kWh
- [tex]\(20^\circ\)[/tex] → 390 kWh
- [tex]\(30^\circ\)[/tex] → 410 kWh
- [tex]\(40^\circ\)[/tex] → 385 kWh
- [tex]\(50^\circ\)[/tex] → 360 kWh
- [tex]\(90^\circ\)[/tex] → 220 kWh

The highest annual energy-output is 410 kWh at a tilt angle of [tex]\(30^\circ\)[/tex].

### Question 4.2: Which factors were kept constant (controlled variables) during this experiment?

During this experiment, the following factors were kept constant:
- Type of solar panels: All panels used were of the same type to ensure consistency in the output.
- Location/field of installation: All panels were installed in the same field, making sure that geographical and climatic conditions were identical for each panel.
- Duration of measurement (365 days): The measurement period was kept the same for all panels, ensuring that the data was collected over an entire year.

### Question 4.3: Identify the independent variable in this experiment.

The independent variable is the one that is deliberately changed or manipulated in an experiment to observe its effect. In this case, the independent variable is:
- Tilt angle: The tilt angle was varied to assess its impact on the annual energy-output of the solar panels.

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