JEE PYQ: Current Electricity Question 63
Question 63 - 2019 (10 Jan 2019 Shift 2)
The actual value of resistance R, shown in the figure is $30,\Omega$. This is measured in an experiment as shown using the standard formula $R = V/I$, where V and I are the reading of the voltmeter and ammeter, respectively. If the measured value of R is 5% less, then the internal resistance of the voltmeter is:
(1) $600,\Omega$
(2) $570,\Omega$
(3) $35,\Omega$
(4) $350,\Omega$
Show Answer
Answer: (2)
Solution
$0.95 R = \frac{R \cdot R_V}{R + R_V}$ (measured value is less as voltmeter is in parallel). $0.95 \times 30 = \frac{30 \cdot R_V}{30 + R_V}$. $0.95 \times 30 = 0.05 R_V$… Actually: $28.5(30 + R_V) = 30 R_V$. $28.5 \times 30 = 1.5 R_V$. $R_V = 570,\Omega$.
BETA
