# How To Draw Scientific Graphs Correctly in Physics Practical Assessments

In this post, we explain how you should draw graphs in your Physics pracs.

## What are scientific graphs?

• A graph is a visual representation of a relationship between two variables, x (independent variable) and y (dependent variable).
• The graphs make it easy to identify trends in data that we have collected.
• An example of a correctly drawn graph is shown below:

## How to draw a scientific graph

 Step Action Detail 1 Identify the variables Place your independent variable on the x-axis of your graph and the dependent variable on the y-axis. 2 Determine the variable range Subtract the lowest data value from the highest data value 3 Determine the scale of the graph Determine a scale, (the numerical value for each square), that best fits the range of each variable. Use a scale that allows your data to be graphed as large as possible in the space provided. The range of each axis may be different. They should each be large enough to cover the needed range without lots of extra space. They do not need to start at zero but it is recommended as this allows you to extrapolate. The scale of each axis may be different, but each one must be consistent. If one box represents one metre at the beginning of the graph, one box always represents one metre 4 Number and label each axis Clearly label the x and y axes including the units of measurement. 5 Plot the data points Plot each data value on the graph with a cross (x) 6 Draw the graph Identify a trend or a relationship between the independent and dependent variables. Remove any outliers for consideration. Draw a curve or a line that best describes the identified trend. Most graphs of experimental data in Physics are linear and not drawn as “connect­ the ­dots”. If required to extrapolate (extend the graph, along the same slope, above or below measured data), use dotted line. 7 Provide a descriptive title Your title should clearly communicate what the graph is about.

## Common mistakes

• Graph 1 shown below is missing labels.

Mistakes in this graph include:

• Missing labels for the axes.
• Missing descriptive title.
• Extrapolated line is not drawn using a dotted line.

6 Common Mistakes HSC Physics Students Make in Exams

Graph 2 shown below contains inappropriate use of scale.

Mistakes in this graph include:

• Incorrect scale.
• Inappropriate use of the scale in x and y-axes. Each box should represent the same value across each axes. For example, if each box is set a value of 0.05 at the beginning of the graph, then one box should always represent 0.05 throughout the axes.
• The student should either start the scale at 0 or at 0.20.