15

ACTIVITY – 0 3

PLOT A GRAPH FROM GIVEN DATA

Aim :  To plot a graph of current versus potential difference with proper choice of scales & error bars.

Apparatus : Graph papers, pencil, scale, etc.

Procedure :                                       PART (A)

      Draw the thick horizontal line as X-axis and Draw the thick vertical line as Y-axis .

      On X  draw independent variable  and Y axis  dependent variable is plotted and on both axis  variables  should be labelled with words and with unit.

      The scale should be chosen so that it is easy to read and so that it makes the data occupy more than half of the paper. Each division on the graph paper represents a simple fraction or multiple of the unit of quantities to be plotted.

      Write the scale top right hand corner.

      Data should be plotted as precisely as possible with sharp pencil and a small dot with circle around it.

      After plotting all the points, do not merely join them one after another but draw a smooth curve or straight line so that it passes through most of the points.

      If the points plotted appear to be nearly in a straight line, draw a straight line passing exactly through most of points and symmetrically through the rest. If the points do not appear to be in a straight line, draw the straight line so that the number of points lie exactly on it and rest are evenly distributed on either side of it.

Observation table (Given Data) :

Sr No	Volt (V)	Current I  mA	Current I     A	Resistance R=V/I  W	Mean R W
1
2
3
4
5
6
7
8
9
10

Calculation and Graph:

                                    PART (B) :GRAPH WITH  ERROR BARS :

The set of data given will have some uncertainties. These are shown on a graph with 'Error Bars'. This is used to find uncertainties in slope and intercept.

Procedure :

         Consider a point with co-ordinates X + DX and Y +  DY.

         Plot a point circled at the point (X, Y)

         Draw the lines from the circle to X + DX, X - DX, Y +  DY and Y -  DY and put bars to the lines. These are called error bars.

         Error bars for data points are of two types

         Error bars in horizontal and vertical as shown in fig as  =a

         Error bars only in vertical as shown in fig as a

      According to data, plot the points with error bars as shown on graph paper (No. (2))

     Draw solid line on the graph is the best fit to the data. Each person could have a different line for the best fit.

Observation table (Given Data) :

Sr No	Volt (V)	Current I  mA	Current I     A	Resistance R=V/I  W	Mean R W
1
2
3
4
5
6
7
8
9
10

Calculation and Graph:

Conclusion :

      Slope of graph without error bars  hence resistance = ………… ohm.

      The slope of graph using error bars and hence resistance = 16.12 ohm.

J K L