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Physics NEET MCQ
Quiz 1
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Q.1
Measure of two quantities along with the precision of respective measuring instrument is $A=2.5\ m/s\pm 0.5\ m/s$ $A=0.10\ m/s\pm 0.01\ m/s$ The value of A B will be
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(0.25 ± 0.135) m
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(0.25 ± 0.05) m
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(0.25 ± 0.5) m
0%
(0.25 ± 0.08) m
Explanation
Solution (the source text for this question lost its multiplication sign and mislabeled the second quantity as "A" instead of "B" — reconstructing from the numbers, this is A × B for A = 2.5 ± 0.5 m/s and B = 0.10 ± 0.01 m/s): Central value: A × B = 2.5 × 0.10 = 0.25 For a product, relative errors add: ΔA/A + ΔB/B = 0.5/2.5 + 0.01/0.10 = 0.20 + 0.10 = 0.30 (30%) Absolute error = 0.30 × 0.25 = 0.075 ≈ 0.08 (to the same precision as the answer) So A × B = (0.25 ± 0.08) m.
Q.2
In the following questions, a statement of assertion is followed by a statement of reason. You are required to choose the correct one out of the given five responses and mark it as (a) If both assertion and reason are true and reason is the correct explanation of the assertion. (b) If both assertion and reason are true but reason is not correct explanation of the assertion. (c) If assertion is true, but reason is false. (d) If both assertion and reason are false. (e) If reason is true but assertion is false. Assertion: SI units are logical and coherent. Reason: SI system of units is a rationalised system.
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a
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b
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c
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d
0%
e
Explanation
Solution: Both statements are individually true: the SI system genuinely is logical and coherent (its derived units come from simple products/quotients of base units with no extra numerical factors), and it genuinely is a rationalised system (rationalisation specifically refers to how SI eliminates stray factors of 4π from many electromagnetic equations by choosing unit definitions carefully). But "rationalised" and "coherent" describe two separate, independent properties of the unit system — being rationalised is not what MAKES the system coherent, so the Reason, while true, is not the correct explanation of the Assertion.
Q.3
The dimensional formula of magnetic flux is
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$[M^0L^{-2}T^{-2}A^{-2}]$
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$[{\rm ML}^2T^{-1}A^3]$
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$\left[{\rm ML}^2T^{-2}A^{-1}\right]$
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$[{\rm ML}^0T^{-2}A^{-2}]$
Explanation
Solution: Magnetic flux Φ = B × A (magnetic field × area). The magnetic field B has dimensional formula [M T⁻² A⁻¹] (from F = qvB, rearranged: B = F/(qv)). Area A has dimensional formula [L²]. So Φ = B × A has dimensional formula [M L² T⁻² A⁻¹].
Q.4
“Parsec” is the unit of
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time
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distance
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angular acceleration
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frequency
Explanation
Solution: A parsec is a unit of astronomical distance (about 3.26 light-years), defined as the distance at which 1 astronomical unit subtends an angle of one arcsecond. It is not a unit of time, angular acceleration, or frequency.
Q.5
The number of significant figures in 3400 is
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12
0%
6
0%
7
0%
2
Explanation
Solution: Trailing zeros in a number written WITHOUT a decimal point (like 3400) are not counted as significant — only the non-zero leading digits are. So 3400 has 2 significant figures (the '3' and the '4').
Q.6
Consider the following equation of Bernoulli’s theorem $P=\frac{1}{2}\rho v^2+\rho gh=K(conatant)$ The dimensions of K/P are same as that of which of the following?
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Thrust
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Angle
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Pressure
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Coefficient of viscosity
Explanation
Solution: The equation itself states P = ½ρv² + ρgh = K (a constant) — so K and P are literally the SAME quantity (K = P). That makes the ratio K/P = 1, a pure number with no dimensions. Among the options, the only dimensionless quantity is Angle (an angle in radians is arc-length ÷ radius — a ratio of two lengths, so its dimensions cancel out). Thrust, Pressure, and Coefficient of viscosity all carry real physical dimensions, so they can't match a dimensionless ratio.
Q.7
The number of significant figures in 0.06900 is
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4
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3
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5
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2
Explanation
Solution: Leading zeros (the '0' before the decimal point and the first two zeros after it, in '0.069 00') are never significant — they just mark the decimal position. But trailing zeros written AFTER a decimal point ARE significant, since writing them is a deliberate statement of precision. So in 0.06900, the significant digits are 6, 9, 0, 0 — 4 significant figures.
Q.8
In the following questions, a statement of assertion is followed by a statement of reason. You are required to choose the correct one out of the given five responses and mark it as (a) If both assertion and reason are true and reason is the correct explanation of the assertion. (b) If both assertion and reason are true but reason is not correct explanation of the assertion. (c) If assertion is true, but reason is false. (d) If both assertion and reason are false. (e) If reason is true but assertion is false. Assertion: The dimensional formula for product of resistance and conductance is same as for dielectric constant. Reason: Both have dimensions of time constant.
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a
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b
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c
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d
0%
e
Explanation
Solution: Resistance (R) and conductance (G) are reciprocals of each other (G = 1/R), so their product R × G = 1 — a pure number with NO dimensions at all. Dielectric constant (relative permittivity) is also dimensionless, being a ratio of two permittivities. So the Assertion — that R×G shares the same dimensional formula as dielectric constant — is TRUE (both are dimensionless). But the Reason claims both have "dimensions of time constant" — a time constant has dimensions of TIME [T], not "dimensionless". Since dimensionless ≠ [T], the Reason is FALSE. So: Assertion true, Reason false.
Q.9
Which of the following group the different dimensions?
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Potential difference, EMF, voltage
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Heat, energy, work-done
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Dipole moment, electric-flux, electric field
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Pressure, stress, Young’s modulus
Explanation
Solution: Check each group for a shared dimension: • Potential difference, EMF, voltage — these are all the same physical quantity by different names, so all three share one dimension. • Heat, energy, work done — all are forms of energy, sharing the dimension [ML²T⁻²]. • Pressure, stress, Young's modulus — all are force per unit area, sharing [ML⁻¹T⁻²]. • Dipole moment, electric flux, electric field — these are three genuinely distinct physical quantities with three DIFFERENT dimensional formulas (charge×length; field×area; force/charge respectively). This is the group whose members do not share a common dimension.
Q.10
The dimensions of $\frac{1}{\sqrt{\mu_0\varepsilon_0}}$ are
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$[I^0M^0L^{-1}T^1]$
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$[I^2M^4L^{-3}T^1]$
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$\left[I^0M^0L^1T^{-1}\right]$
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$\left[I^{-2}T^{-2}L^1M^1\right]$
Explanation
Solution: This combination is a well-known result in electromagnetism: 1/√(μ₀ε₀) equals c, the speed of light in vacuum. Speed has the dimensional formula [L¹T⁻¹], with no mass or current dimension involved — so [M⁰L¹T⁻¹], written with the current dimension shown explicitly as I⁰M⁰L¹T⁻¹.
Q.11
What are the dimensions of electrical permittivity?
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$M^{-1}L^2T^3Q^{-1}$
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$M^{-2}L^{-3}T^2Q^2$
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${\rm ML}^{-2}T^2Q^{-2}$
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$M^{-1}L^3T^2Q^{-2}$
Explanation
Solution: From Coulomb's law, F = q₁q₂ / (4πε₀r²), rearranged: ε₀ = q² / (F·r²) (using charge Q as a base dimension). [F] = [MLT⁻²], [r²] = [L²], [q²] = [Q²] ε₀ = Q² / (MLT⁻² · L²) = Q² / (ML³T⁻²) = M⁻¹L⁻³T²Q² (Note: the marked option prints M⁻², which looks like a scraping/typo error for M⁻¹ — the correctly derived, standard dimensional formula for permittivity is M⁻¹L⁻³T²Q² (equivalently M⁻¹L⁻³T⁴A² in terms of current); only the exponent of M in the printed option appears to be off by one.)
Q.12
Which of the following pair has different dimensions?
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Electric pressure, energy density
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Intensity, $\epsilon_0{E_0}^2c$
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Reynold’s number and time constant
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Work, Torque
Explanation
Solution: Check each pair: • Electric pressure and energy density — in field theory these are literally the same quantity (electric pressure = field energy density), so same dimension. • Intensity and ε₀E₀²c — the standard formula for EM wave intensity IS (1/2)ε₀E₀²c, so these are proportional and share the same dimension. • Work and Torque — both are force × distance, sharing [ML²T⁻²]. • Reynold's number and time constant — Reynold's number is a pure, DIMENSIONLESS ratio (it has no units at all), while a time constant has the dimension of TIME [T]. These clearly do NOT share a dimension — this is the mismatched pair.
Q.13
The pressure on a square plate is measured by measuring the force on the plate and the length of the sides of the plate by using the formula $p =\frac{F}{l^2}$. If the maximum errors in the measurement of force and length are 4% and 2% respectively, then the maximum error in the measurement of pressure is
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2%
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8%
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1%
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10%
Explanation
Solution: p = F / l². For a quotient/power combination like this, relative errors combine as: (Δp/p) = (ΔF/F) + 2×(Δl/l) — the exponent 2 on l means its relative error counts twice. Given ΔF/F = 4% and Δl/l = 2%: Δp/p = 4% + 2×2% = 4% + 4% = 8%.
Q.14
The heat produced in a long wire is charactrised by resistance, current and time through which the current passes. If the errors in measuring these quatities are respectively 1%, 2% and 1%, then total error in calculating the energy produced is
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4%
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6%
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8%
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3%
Explanation
Solution: Heat/energy produced by a current follows H = I²Rt. For this combination, relative errors combine as: ΔH/H = 2×(ΔI/I) + (ΔR/R) + (Δt/t) — the exponent 2 on I means its error counts twice. Given ΔR/R = 1%, ΔI/I = 2%, Δt/t = 1%: ΔH/H = 2×2% + 1% + 1% = 4% + 1% + 1% = 6%.
Q.15
If the energy $E=G^ph^qc^r$ where $G$ is the universal gravitational constant, $h$ is the Planck’s constant and $c$ is the velocity of light, then the values of $p$, $q$ and $r$ are, respectively
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–1/2, 1/2 and 3/2
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1/2, –1/2 and –5/2
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1/2, –1/2 and –3/2
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–1/2, 1/2 and 5/2
Explanation
Solution: E = Gᵖ hᵠ cʳ. Matching dimensions on both sides: [G] = M⁻¹L³T⁻², [h] = ML²T⁻¹, [c] = LT⁻¹, [E] = ML²T⁻² Mass: −p + q = 1 Length: 3p + 2q + r = 2 Time: −2p − q − r = −2 From the mass equation: q = 1 + p. Substituting into the length equation: 3p + 2(1+p) + r = 2 → 5p + r = 0 → r = −5p. Substituting both into the time equation: −2p − (1+p) − (−5p) = −2 → 2p − 1 = −2 → p = −1/2. Then q = 1 + (−1/2) = 1/2, and r = −5×(−1/2) = 5/2. So p = −1/2, q = 1/2, r = 5/2.
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