CBSE Class 10 Science 2019 Delhi Set 1

Question : 26

Total: 28

While studying the dependence of potential difference (V) across a resistor on the current (l) 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 1 . 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.
OR
What would you suggest to a student if while performing an experiment he finds that the pointer/needle of the ammeter and voltmeter do not coincide with the zero marks on the scales when circuit is open? No extra ammeter/voltmeter is available in the laboratory.

Solution:

The straight line in the graph signify that potential difference and current are directly proportional to each other.
The method of determining resistance of resistor using the graph is by Ohm's law, V=IR and by calculating the slope from the points mentioned on the graph

∴‌‌R=‌

‌ Slope of ‌V−‌ I graph ‌

OR
This is called the zero error of the scale of ammeter or voltmeter. If there is a zero error then this error is subtracted from the value that depicts when the circuit is closed otherwise accurate readings will not be recorded.

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