Unit and Measurement MCQ Questions & Answers in Basic Physics | Physics
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171.
The displacement of a body at a particular second $$n$$ is given by the expression $${S_{{\text{nth}}}} = u + \frac{a}{2}\left( {2n - 1} \right).$$ The dimensional formula of $${S_{{\text{nth}}}}$$ in this equation is
172.
Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage errors in the measurement of the current and the voltage difference are $$3\% $$ each, then error in the value of resistance of the wire is
A
$$6\% $$
B
zero
C
$$1\% $$
D
$$3\% $$
Answer :
$$6\% $$
From Ohm’s law,
$$\eqalign{
& \Rightarrow R = \frac{V}{I} \Rightarrow \ln R = \ln V - \ln I \cr
& \Rightarrow \frac{{\Delta R}}{R} = \frac{{\Delta V}}{V} + \frac{{\Delta I}}{I} = 3\% + 3\% = 6\% \cr} $$
173.
A physical quantity $$Q$$ is related to four observables $$x, y, z$$ and $$t$$ by the relation $$Q = \frac{{{x^{\frac{2}{5}}}{z^3}}}{{y\sqrt t }}.$$ The percentage errors of measurement in $$x, y, z$$ and $$t$$ are $$2.5\% ,2\% ,0.5\% $$ and $$1\% $$ respectively. The percentage error in $$Q$$ will be
174.
Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage errors in the measurement of the current and the voltage difference are $$3\% $$ each, then error in the value of resistance of the wire is :