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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 I. He got a straight line graph passing through the origin. What does the straight line signify?

Solution:

When the student took 5 readings for different values of R and the student gets a straight line graph. This verifies Ohm's law. Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. So, if you plot a graph of current against voltage you will get: I∝V
I = V/R
R = V/I