The actual value of resistance R , shown in the figure is 30 Ω . This is measured in an experiment as shown using the standard formula R = V I , where V and I are the readings of the voltmeter and ammeter, respectively. If the measured value of R is 5 % less, then the internal resistance of the voltmeter is:

Step-by-step solution

Measured value of R = 5 % less than actual value of R i.e., R ' = 30 - ( 5 % of 30 ) = 30 - 5 100 × 30 R ' = 28 . 5   Ω . . . i Now, let us assume that internal resistance of voltmeter R V . Replacing voltmeter with its internal resistance, we get following circuit. It is clear that the measured value, R ' should be equal to parallel combination of R and R V . Mathematically, R ' = R × R V R + R V = 28 . 5   Ω Given. R = 30   Ω ⇒   30   R V 30