MCQ
Two identical moving coil galvanometer have $10 \Omega$ resistance and full scale deflection at $2 \mu A$ current. One of them is converted into a voltmeter of $100 mV$ full scale reading and the other into an Ammeter of $1 mA$ full scale current using appropriate resistors. These are then used to measure the voltage and current in the Ohm's law experiment with $R =1000 \Omega$ resistor by using an ideal cell. Which of the following statement( $s$ ) is/are correct?

$(1)$ The measured value of $R$ will be $978 \Omega$

$(2)$ The resistance of the Voltmeter will be $100 k \Omega$.

$(3)$ The resistance of the Ammeter will be $0.02 \Omega$ (round off to $2^{\text {nd }}$ decimal place)

$(4)$ If the ideal cell is replaced by a cell having internal resistance of $5 \Omega$ then the measured value of $R$ will be more than $1000 \Omega$.

  • A
    $1,2$
  • B
    $1,4$
  • C
    $2,3$
  • D
    $1,3$

Answer

(image)

$0.1=2 \times 10^{-6}\left(10+R_V\right)$

$\therefore R_V=49990 \Omega$

(image)

$2 \times 10^{-6} \times 10=10^{-3} R _{ A } \therefore R _{ A }=0.02 \Omega$

(image)

$y 50000=(x-y) 1000$

$\therefore 51 y=x$

Reading $=\frac{y 50000}{x} \approx 980$

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