2-Dimensional Graph
Theory:
1) A two dimensional graph is generally drawn in the first quadrant.
2) A graph has a horizontal x-axis and a vertical y-axis.
3) The values plotted on a graph are variables.
4) The controllable variable i.e. the one which is independent is drawn on the x-axis. This
variable is completely under control of the observer.
5) The dependent variable is drawn on the y-axis.
6) A graph usually begins with the origin i.e. x-axis and y-axis both start from origin.
7) If the variable chosen is such that it can have negative values either in the x or y axis, the
graph is shown to be extending beyond origin. For any variables for which this is not true there
is no point in extending the line beyond the origin.
8) Decide a perfect scale using which the observed variables can be plotted on the graph. Write
the numbers using that scale below the x-axis and on the left of the y-axis (avoid writing
numbers inside the first quadrant.
9) The scale could be same or different for both x and y axes.
10) The scales used for both the x and y axes has to be written either in the space given on a
graph paper or on the top right corner of the graph paper as, 1 cm = _____ units for both x and
y axes. If the units are known it is needed to be mentioned.
11) Write the name of variables that is measured on x and y axes below the numbers written
for each axis. Write the units of the variables inside a bracket right next to the name of the
variable.
12) If there is no fixed unit for the variable measured or if the values are abstract write as
(arbitrary units) or (a. u.) beside the names of the variables.
13) Plot the points on the 2-dimensional graph by observing the ordinate (y-coordinate) for a
given abscissa (x-coordinate).
14) Once the points are plotted join the points to observe the nature of graph or curve.
15) If the nature of the graph is linear try to draw a straight line using a scale. If the points are
not in a line, try to draw a straight line such that maximum number of points lie on the drawn
straight line.
16) Two points always make a straight line hence try to fit a minimum of three points to draw
a straight line.
17) If there are no three points which could lie on a straight line in a linear graph, try to draw
a line such that the points plotted on the graph are evenly distributed on both sides of the line.
18) For graphs showing a curve ensure that no sudden change in angles are made or drawn in
the graph (unless they are calculated to be so).
19) For values which are having measured values far from the origin for any one of the axis,
an axis break (a zig-zag line) or a graph break is used to indicate.
20) Graphs should never be outlined.
21) The slope of a curve is calculated by drawing a tangent to a curve at that point or for a
straight line graph it is calculated by choosing any two points and using the formula for slope.
22) The slope of graph drawn at any point gives the rate of change of dependent variable with
respect to the independent variable.
SKILL
Title: Drawing a 2-dimensional graph
Skills/competencies to be acquired:
1) To understand the basics of graph drawing.
2) To understand the nature of a plotted graph.
3) To understand the fitting nature of a graph.
Duration: 1 hour
1. What is the purpose of this activity?
Ans: To learn a skill and understand the basics of plotting a graph for any data acquired through
experimentation. This activity is also helpful in understanding the importance of graph plotting
and fitting.
2. Steps performed in this activity.
Ans: a) Reading through the points given in theory.
b) Plotting graphs for given values.
c) Understanding the nature of graph and deriving conclusions.
3. What resources/materials/equipments/tools dd you use for this activity?
Ans: Graph paper, pencil, scale
4. What skills did you acquire?
(a) Learnt to draw 2-dimensional graphs.
(b) Learnt the fitting of the curves and lines.
5. Time taken to complete the activity? 1 hour.
Q) Plot the graph for the following data:
Time
(minutes)
Temperature (oC)
0
3
6
9
12
15
18
21
24
27
30
31
33
36
41
49
60
75
94
99
99
99
Q) Does the rate of heating increase or decrease?