Question

Assertion : The resistance of an ideal voltmeter should be infinite.
Reason : The potential difference measured by a voltmeter across a resistor is always less than the actual potential difference across the resistor.

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

Answer 1

The correct option is B Both (A) and (R) are true but (R) is not the correct explanation of A.

To measure the correct P.D across the load, the total current must pass through the load. Therefore the resistance of the voltmeter should be very high. For an ideal voltmeter, it should be infinite.

In practice, the current passing through the load is less than the total current as a small fraction of current passes through the voltmeter. Thus when measured the P.D is less than the actual voltage.

The given statements are independent facts and the statement 2 is not the correct explanation for the assertion given.