Question

Given below are two statements : One is labelled as Assertion \(A\) and the other is labelled as Reason R 
Assertion A : For measuring the potential difference across a resistance of \(600 \Omega\), the voltmeter with resistance \(1000 \Omega\) will be preferred over voltmeter with resistance \(4000 \Omega\).
Reason R : Voltmeter with higher resistance will draw smaller current than voltmeter with lower resistance.
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both \(A\) and \(R\) are correct but \(R\) is not the correct explanation of \(A\)
• B. Both \(A\) and \(R\) are correct and \(R\) is the correct explanation of \(A\)
• C. A is not correct but \(R\) is correct
• D. A is correct but \(R\) is not correct

Hint:

Remember that an ideal voltmeter has infinite resistance. A practical voltmeter should have as high a resistance as possible to minimize the impact on the circuit being measured.

Answer 1

The Correct Option is C

Step 1: Analyze Assertion A
An ideal voltmeter has infinite resistance. A real voltmeter should have a resistance much higher than the resistance it is measuring across to minimize the current drawn by the voltmeter and ensure an accurate reading of the potential difference. In this case, measuring across a 600 Ω resistor, a voltmeter with 4000 Ω resistance is preferred over a voltmeter with 1000 Ω resistance because it’s closer to the ideal. Thus, the assertion is incorrect.

Step 2: Analyze Reason R
A voltmeter is connected in parallel to the resistor it is measuring. According to Ohm's law, \( V = IR \), the current (\( I \)) drawn by a voltmeter is inversely proportional to its resistance (\( R \)) if the voltage (\( V \)) is constant. Therefore, a voltmeter with higher resistance will draw a smaller current. Thus, the reason is correct.

Conclusion: Assertion A is incorrect, but Reason R is correct. Thus, the correct option is (3).