Q. What is a graph and procedure to select suitable scales for representing independent and dependent variable quantities along their respective axis while plotting a graph between them.
Graph
A graph is straight or curved line which illustrates the relationship of two inter dependent quantities.
Procedure for Drawing Graph
(1) Two mutually perpendicular lines XOX’ and YOY’ are drawn on the graph paper. These lines are called axis. The point of intersection of these lines is known as origin. While drawing a graph between two quantities the independent variable is usually taken along the X-axis. Positive values of the quantities are taken along right side of the origin and negative along the left side. Similarly dependent variable is represented along V-axis. Positive values are plotted along the line above the origin and negative ones below the origin. A suitable scale is selected to show the value of independent variable quantities and dependent variable quantities. For this the maximum and minimum value of the quantity is taken into account.
Let us explain this procedure by considering the example of helical spring experiment. In this experiment a spring having a pan is hung vertically by a stand. By putting a 10gm mass in the pan the spring is stretched. By noting the reading of the pointer against the scale S before and after adding the weight, the increase in length can be measured. By adding an additional mass of 10gm and noting the reading of the pointer on the scale we can find the corresponding extension of masses of 20, 30, 40 and 50 grams.
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