Technical Based Test Test 1 Nddc Scholarship
Question 51
Torque is defined as
Answer: D. All of these
Torque is defined in several equivalent ways:
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As the product of force and moment arm (option A),
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As the turning effect of a force (option B),
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And mathematically as the cross product of position vector and force (option C):
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Question 52
Resistivity of a wire depends on ______
Correct answer: B. material
The resistivity of a wire is a material property and does not depend on its length or cross-sectional area.
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Question 53
If a wire 30cm long is extended to 30.5cm by a force of 300N. Find the strain energy of the wire.
\[\textbf{Correct answer:} \ D. \ 0.75 \ \text{J}\]
\[\text{Extension:} \ e = 30.5 - 30 = 0.5 \ \text{cm} = 0.005 \ \text{m} \]
\[\text{Strain energy:} \ U = \dfrac{1}{2} \times F \times e \]
\[U = \dfrac{1}{2} \times 300 \times 0.005 = 0.75 \ \text{J}\]
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Question 54
A metal of volume 40cm3 is heated from 30oC to 90oC, the increase in volume is [Linear expansivity of the metal= 2.0 x 10-5K-1]
The formula for volume expansion is:$$\Delta V = 3 \alpha V \Delta T$$ $$\alpha = 2.0 \times 10^{-5} \, \text{K}^{-1}$$ $$V = 40 \, \text{cm}^3$$ $$\Delta T = 90^\circ \text{C} - 30^\circ \text{C} = 60 \, \text{K}$$
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Question 55
If the volume of a gas increases steadily as the temperature decreases at constant pressure, the gas obeys
Answer D. pressure law
At constant pressure, a steady increase in volume as temperature decreases contradicts Charles’ law, so the relation instead matches the pressure law, which links temperature and pressure for a fixed volume.
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Question 56
The temperature of the system decreases in an.
Answer D. adiabatic expansion
In adiabatic expansion, the gas does work without heat exchange, causing its internal energy — and thus temperature — to decrease.
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Question 57
Lenz’s law is a law of the conservation of
Answer A. energy
Lenz’s law ensures that the induced current opposes the change causing it, thereby conserving energy.
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Question 58
The dimensions of electromotive force are
Answer A. ML²T⁻³I⁻¹
Electromotive force (emf) is measured in volts, which is joules per coulomb. A joule has dimensions ML2T−2, and a coulomb has IT, giving ML2T−3I−1
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Question 59
If 16mA of current flows through a conductor in one second, the number of electrons transported per second is
\[\text{Answer B. } 1.00 \times 10^{17} \\[4pt]\] Q = It \[Q = 16 \times 10^{-3} \times 1 = 1.6 \times 10^{-2} \ \mathrm{C} \\[4pt]\]\[n = \dfrac{Q}{e} = \dfrac{1.6 \times 10^{-2}}{1.6 \times 10^{-19}} = 1.0 \times 10^{17}\]
