JEE Physics Units And Measurements MCQs Set 22

Download JEE MCQs for JEE Physics: Units and Measurements

Access targeted multiple-choice questions for Units and Measurements designed to align with the latest JEE academic syllabus for JEE Physics. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Chapter-wise Objective Questions: Units and Measurements

View or download the dedicated Units and Measurements MCQ resource below. Practicing these 50 objective questions regularly builds familiarity with standard exam patterns and helps secure higher marks in final Physics evaluations.

Multiple Choice Questions

Question 1: If \( x=at+bt^2 \), where \( x \) is the distance travelled by the body in kilometres and \( t \) is the time in seconds, then the units of \( b \) are
(a) km/s
(b) km s
(c) km/s\(^2\)
(d) km s\(^2\)
Show Answer & Explanation

Answer: (c) km/s\(^2\)

Explanation:
1. Every term must have the same dimensions: \( [b]=[x]/[t^2] \).

Teacher's Note:
1. Key relation used: \( bt^2 \) has the unit of \( x \), so \( b \) has km/s\(^2\).
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 2: In the equation \( \Big(P+\dfrac{a}{V^2}\Big)(V-b)= \) constant, the units of \( a \) are
(a) dyne cm\(^5\)
(b) dyne cm\(^4\)
(c) dyne/cm\(^3\)
(d) dyne/cm\(^2\)
Show Answer & Explanation

Answer: (b) dyne cm\(^4\)

Explanation:
1. \( a/V^2 \) must be a pressure.

Teacher's Note:
1. Key relation used: \( [a]=[P][V^2] \) = dyne cm\(^{-2}\) \( \times \) cm\(^6\) = dyne cm\(^4\).
2. Check the direction of each proportionality (direct or inverse) before substituting numbers.

Question 3: Which of the following quantities is expressed as force per unit area?
(a) work
(b) pressure
(c) volume
(d) area
Show Answer & Explanation

Answer: (b) pressure

Explanation:
1. Its unit is the pascal.

Teacher's Note:
1. Key relation used: Pressure \( =F/A \).
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 4: The unit of impulse is
(a) newton
(b) kg m
(c) kg m/s
(d) joule
Show Answer & Explanation

Answer: (c) kg m/s

Explanation:
1. Unit: N s = kg m/s.

Teacher's Note:
1. Key relation used: Impulse \( =F\Delta t \) = change in momentum.
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 5: The correct value of \( 0^\circ \)C on the Kelvin scale is
(a) 273.15 K
(b) 272.85 K
(c) 273 K
(d) 273.2 K
Show Answer & Explanation

Answer: (a) 273.15 K

Explanation:
1. \( T(\text{K})=t(^\circ\text{C})+273.15 \).

Teacher's Note:
1. Key relation used: The accepted value is 273.15 K.
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 6: 'Torr' is the unit of
(a) pressure
(b) volume
(c) density
(d) flux
Show Answer & Explanation

Answer: (a) pressure

Explanation:
1. Used for vacuum pressure.

Teacher's Note:
1. Key relation used: 1 torr \( =1 \) mm of Hg \( \approx133.3 \) Pa.
2. Check the direction of each proportionality (direct or inverse) before substituting numbers.

Question 7: Which of the following is a derived unit?
(a) unit of mass
(b) unit of length
(c) unit of time
(d) unit of volume
Show Answer & Explanation

Answer: (d) unit of volume

Explanation:
1. Mass, length and time are base units.

Teacher's Note:
1. Key relation used: Volume is \( \text{length}^3 \).
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 8: The units of angular momentum are
(a) kg m\(^2\) s\(^{-2}\)
(b) joule second
(c) joule/second
(d) kg m s\(^{-2}\)
Show Answer & Explanation

Answer: (b) joule second

Explanation:
1. Angular momentum has the dimensions of action.

Teacher's Note:
1. Key relation used: \( L=mvr \): kg m\(^2\) s\(^{-1}\) = J s.
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 9: The S.I. unit of gravitational potential is
(a) J
(b) J kg\(^{-1}\)
(c) J kg
(d) J kg\(^{-2}\)
Show Answer & Explanation

Answer: (b) J kg\(^{-1}\)

Explanation:
1. \( V=-GM/r \).

Teacher's Note:
1. Key relation used: Potential is energy per unit mass.
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 10: In C.G.S. system the magnitude of a force is 100 dynes. In another system where the fundamental physical quantities are kilogram, metre and minute, the magnitude of the force is
(a) 0.036
(b) 0.36
(c) 3.6
(d) 36
Show Answer & Explanation

Answer: (c) 3.6

Explanation:
1. \( 10^{-3}\times3600=3.6 \).

Teacher's Note:
1. Convert the unit of time carefully: 1 min = 60 s.

Question 11: The unit of \( L/R \) (where \( L \) = inductance and \( R \) = resistance) is
(a) sec
(b) sec\(^{-1}\)
(c) volt
(d) ampere
Show Answer & Explanation

Answer: (a) sec

Explanation:
1. Henry per ohm equals second.

Teacher's Note:
1. Key relation used: \( L/R \) is the time constant of an LR circuit.
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 12: Which is different from the others by units?
(a) phase difference
(b) mechanical equivalent of heat
(c) loudness of sound
(d) Poisson's ratio
Show Answer & Explanation

Answer: (b) mechanical equivalent of heat

Explanation:
1. The other three are pure numbers (or quasi-units like decibel).

Teacher's Note:
1. Key relation used: The mechanical equivalent of heat has the units J/cal.
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 13: Length cannot be measured in
(a) fermi
(b) debye
(c) micron
(d) light year
Show Answer & Explanation

Answer: (b) debye

Explanation:
1. Others are length units.

Teacher's Note:
1. Key relation used: The debye is a unit of electric dipole moment.
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 14: The value of Planck's constant is
(a) \( 6.63\times10^{-34} \) J s
(b) \( 6.63\times10^{34} \) J/s
(c) \( 6.63\times10^{-34} \) J s\(^{-1}\)
(d) \( 6.63\times10^{34} \) kg m\(^2\) s
Show Answer & Explanation

Answer: (a) \( 6.63\times10^{-34} \) J s

Explanation:
1. Its dimensions are ML\(^2\)T\(^{-1}\).

Teacher's Note:
1. Key relation used: \( h=6.63\times10^{-34} \) J s.
2. Check the direction of each proportionality (direct or inverse) before substituting numbers.

Question 15: A physical quantity is measured and its value is found to be \( nu \), where \( n \) = numerical value and \( u \) = unit. Which of the following relations is true?
(a) \( n\propto u^2 \)
(b) \( n\propto u \)
(c) \( n\propto\sqrt u \)
(d) \( n\propto\dfrac1u \)
Show Answer & Explanation

Answer: (d) \( n\propto\dfrac1u \)

Explanation:
1. A larger unit gives a smaller numerical value.

Teacher's Note:
1. Key relation used: \( nu=\) constant.
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 16: Candela is the unit of
(a) electric intensity
(b) luminous intensity
(c) sound intensity
(d) none of these
Show Answer & Explanation

Answer: (b) luminous intensity

Explanation:
1. It measures luminous intensity.

Teacher's Note:
1. Key relation used: It is one of the seven SI base units.
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 17: The unit of reactance is
(a) ohm
(b) volt
(c) mho
(d) newton
Show Answer & Explanation

Answer: (a) ohm

Explanation:
1. \( X_L=\omega L \).

Teacher's Note:
1. Key relation used: Reactance has the same unit as resistance.
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 18: The number of base SI units is
(a) 4
(b) 7
(c) 3
(d) 5
Show Answer & Explanation

Answer: (b) 7

Explanation:
1. Seven.

Teacher's Note:
1. Key relation used: m, kg, s, A, K, mol, cd.
2. Check the direction of each proportionality (direct or inverse) before substituting numbers.

Question 19: The SI unit of permittivity is
(a) C\(^2\) m\(^2\) N\(^{-1}\)
(b) C\(^{-1}\) m\(^{-2}\) N\(^{-2}\)
(c) C\(^2\) m\(^{-2}\) N\(^{-1}\)
(d) C\(^{-2}\) m\(^{-2}\) N\(^{-1}\)
Show Answer & Explanation

Answer: (c) C\(^2\) m\(^{-2}\) N\(^{-1}\)

Explanation:
1. Rearrange Coulomb's law.

Teacher's Note:
1. Key relation used: From \( F=\dfrac{q_1q_2}{4\pi\epsilon_0r^2} \): \( \epsilon_0 \) has unit C\(^2\) N\(^{-1}\) m\(^{-2}\).
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 20: The unit of surface tension is
(a) N m\(^{-1}\)
(b) N m\(^{-2}\)
(c) N\(^2\) m\(^{-1}\)
(d) N m\(^{-3}\)
Show Answer & Explanation

Answer: (a) N m\(^{-1}\)

Explanation:
1. Dimensions MT\(^{-2}\).

Teacher's Note:
1. Key relation used: Force per unit length.
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 21: The unit of Young's modulus is
(a) N m\(^2\)
(b) N m\(^{-2}\)
(c) N m
(d) N m\(^{-1}\)
Show Answer & Explanation

Answer: (b) N m\(^{-2}\)

Explanation:
1. N/m\(^2\).

Teacher's Note:
1. Key relation used: Young's modulus is a stress.
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 22: One femtometre is equivalent to
(a) \( 10^{15} \) m
(b) \( 10^{-15} \) m
(c) \( 10^{-12} \) m
(d) \( 10^{12} \) m
Show Answer & Explanation

Answer: (b) \( 10^{-15} \) m

Explanation:
1. Also called one fermi.

Teacher's Note:
1. Key relation used: femto means \( 10^{-15} \).
2. Check the direction of each proportionality (direct or inverse) before substituting numbers.

Question 23: The dimensional formula \( ML^{-1}T^{-2} \) does not represent the physical quantity
(a) Young's modulus of elasticity
(b) stress
(c) strain
(d) pressure
Show Answer & Explanation

Answer: (c) strain

Explanation:
1. The others are stresses.

Teacher's Note:
1. Key relation used: Strain is dimensionless.
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 24: The dimensional formula \( ML^2T^{-3} \) represents
(a) force
(b) power
(c) energy
(d) work
Show Answer & Explanation

Answer: (b) power

Explanation:
1. \( ML^2T^{-2}/T \).

Teacher's Note:
1. Key relation used: Power \( =W/t \).
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 25: The dimensions of calorie are
(a) \( ML^2T^{-2} \)
(b) \( MLT^{-2} \)
(c) \( ML^2T^{-1} \)
(d) \( ML^2T^{-3} \)
Show Answer & Explanation

Answer: (a) \( ML^2T^{-2} \)

Explanation:
1. Same as joule.

Teacher's Note:
1. Key relation used: Calorie is a unit of energy.
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

Question 26: The quantity whose dimensions are \( ML^2T^{-1} \) is
(a) torque
(b) angular momentum
(c) power
(d) work
Show Answer & Explanation

Answer: (b) angular momentum

Explanation:
1. Torque has \( ML^2T^{-2} \).

Teacher's Note:
1. Key relation used: \( L=mvr \).
2. Check the direction of each proportionality (direct or inverse) before substituting numbers.

Question 27: If \( L \) and \( R \) are respectively the inductance and resistance, then the dimensions of \( L/R \) will be
(a) \( M^0L^0T^{-1} \)
(b) \( M^0L^0T^0 \)
(c) \( M^0L^0T \)
(d) cannot be represented in terms of M, L and T
Show Answer & Explanation

Answer: (c) \( M^0L^0T \)

Explanation:
1. Time constant.

Teacher's Note:
1. Key relation used: \( L/R \) is a time.
2. State the governing law first, then substitute; this avoids sign and power-of-ten slips.

Question 28: If \( C \) and \( R \) represent capacitance and resistance respectively, then the dimensions of \( RC \) are
(a) \( M^0L^0T^2 \)
(b) \( M^0L^0T \)
(c) \( ML^{-1} \)
(d) none of the above
Show Answer & Explanation

Answer: (b) \( M^0L^0T \)

Explanation:
1. Dimension T.

Teacher's Note:
1. Key relation used: \( RC \) is the time constant.
2. After finding the value, test it against the options by a quick order-of-magnitude estimate.

Question 29: The dimensional formula for latent heat is
(a) \( M^0L^2T^{-2} \)
(b) \( MLT^{-2} \)
(c) \( ML^2T^{-2} \)
(d) \( ML^0T^{-1} \)
Show Answer & Explanation

Answer: (a) \( M^0L^2T^{-2} \)

Explanation:
1. Energy per unit mass.

Teacher's Note:
1. Key relation used: \( L=Q/m \).
2. Reduce the data to ratios and keep every quantity in SI units before calculating.

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Multiple Choice Questions (MCQs) for JEE Physics Units and Measurements

About Units and Measurements MCQs for JEE Physics

Test your conceptual understanding of Units and Measurements with these targeted multiple-choice questions. Designed in alignment with the latest JEE curriculum for JEE Physics, these problem sets build accuracy and prepare students for objective exams.

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FAQs

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