Q26 of 27 Page 1

While studying the dependence of potential difference(V) across a resistor on the current(I) passing through it, in order to determine the resistance of a resistor, a student took 5 readings for different values of current and plotted a graph between V and I. He got a straight-line graph passing through the origin. What does the straight line signify? Write the method of determining resistance of the resistor using this graph.

According to Ohm’s law, the potential difference across a conductor is directly proportional to the current flowing through it



where V is the potential difference and I is the current.


The relationship between V and I is linear for a conductor.


To remove the proportionality, we replace it by a constant called R



Here R is the resistance of the conductor and is a fixed value.


If the student plots the potential difference on the x-axis, then the slope of the graph will be



The quantity on y axis is current(I) and on x axis is voltage(V), the slope will be



The resistance will be the reciprocal of the slope.


This straight line signifies that the resistor is a linear element, i.e. it has linear characteristics in a V-I graph.


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