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Question
Answer the following question.
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 the resistor, a student took 5 readings for different values of current and plotted a graph between V and t. He got a straight line graph passing through the origin. What does the straight-line signify? Write the method of determining the resistance of the resister using this graph.
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Solution
The straight-line graph between the potential difference ( V) and current(I) shows that resistor is a linear element and follows Ohm's Law.
Calculation of Resistance: At any point on the graph, resistance is given as,
`"R" = ("V"_° ("value of potential difference at that point"))/("I"_° ("value of current at that point"))`
In other words, the Slope of the graph at any point gives the value `1/"R"`
Hence,
slope `="I"_°/"V"_° = 1/"R"`
`⇒ "R" = 1/"slope" =( "V"_° ("Value of Potential difference at that point"))/("I"_° ("Value of current at that point"))`
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