Reason : Soft iron has high magnetic permeability and cannot be easily magnetized or demagnetized.
(Mass of the proton $=1.67 \times 10^{-27}\, kg$, charge of the proton $=1.69 \times 10^{-19}\,C$)

$(1)$ 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 $1000 \Omega$.


