Question

Two students P and Q perform an experiment to verify Ohm’s law for a conductor with resistance R. They use a current source and a voltmeter with least counts of 0.1mA and 0.1mV respectively. The plots of the variation voltage drop (V) across R with current (i) for both are shown. The statement which is most likely to be correct is?


A) P has only random errors.
B) Q has only systematic errors.
C) Q has both random and systematic errors.
D) P has both random and systematic errors.

Answer 1

We need to closely analyze the graphs of the given quantities current and voltage to understand the possible errors that can arise from the experiment. We need to know the different types of errors involved in an experiment.

Complete step-by-step solution:
We are given the experimental observations of verification of Ohm’s law by measuring the voltage drop and current through a resistor R. Two students have plotted the graphs with their respective observations as shown in the figure.


Let us understand the different types of errors involved in an experiment. The major errors are random errors and systematic errors.
Random errors are those errors, which occur in an experiment without any avoidable reasons due to variation in the parameters involved in the experiment. These types of errors are the reason for varying observations for the same experiment done repeatedly. From the information in the graph given, we can understand both the students have met with random errors as they have different observations for each reading. Random errors are an unavoidable part of experiments.
Systematic errors are those which occur in an experiment due to misalignments and non-calibrations in the setup. These errors are born due to the careless approach of the experimentalist and are to be avoided for better results. We can understand the presence of systematic errors from the graph by checking the sum of the difference between each reading from the mean value. If this sum comes out to be non-zero, then the experiment involves systematic errors. In the above graphs, when we look at the variation of each value from the mean, the student Q’s experiment has the sum not equal to zero. i.e., Q has some systematic errors involved.
So, we understand that both P and Q have random errors and Q has systematic
errors also. The correct answer is option C.

Note: The errors involved in an experiment can result in very minute changes to large misleading inferences. The high precision experiments which involve sub-atomic particles cannot afford slight variation or errors as that can result in unfavorable outcomes.