• Amal Augustine
• November 29, 2025

Significant Figures, Measurement Errors & Units: 40 Essential MCQs for NEET, JEE & CUET

Understanding significant figures, measurement errors, units and dimensional analysis is essential for scoring high in physics-based competitive exams like NEET, JEE, and CUET. These concepts form the foundation of experimental physics and help students analyse accuracy, precision, and reliability of measurements.
This guide covers 40 carefully curated MCQs along with a compact theory overview, targeting commonly tested topics such as least count, significant figures, dimensional formulas, error propagation, measurement instruments, and unit conversions.

Understanding Key Concepts (Quick Revision)

Significant Figures

Significant figures indicate the precision of a measurement. Knowing how many digits are meaningful helps avoid misinterpretation of results, especially when multiplying, dividing or rounding values.

Error Analysis

Error propagation is crucial when calculating physical quantities. Whether absolute, relative, or percentage error, it helps determine the reliability of experimental outcomes.

Units & Dimensions

Competitive exams frequently test conversions between SI, CGS and astronomical units, along with identification of dimensionless quantities and meaningful mathematical operations.

40 MCQs with Answers (NEET–JEE–CUET Level)

1. Which of the following is the most accurate?

a) 200.0 m
b) 20 × 10¹ m
c) 2 × 10² m
d) 0.2 × 10³ m
Answer: a)

2. What is the correct number of significant figures in 0.0003062?

a) Four
b) Seven
c) Eight
d) Six
Answer: a)

3. If Z = A³, then ΔZ/Z = ____

a) ΔA³/A
b) (ΔA/A)³
c) 3(ΔA/A)
d) (ΔA/A)¹/³
Answer: c)

4. When two quantities are divided, the relative error is:

a) Product of individual errors
b) Quotient of individual errors
c) Difference of individual errors
d) Sum of individual errors
Answer: d)

5. If L = 2.331 cm and B = 2.1 cm, then L + B =

a) 4.4 cm
b) 4 cm
c) 4.43 cm
d) 4.431 cm
Answer: a)

6. The unit of percentage error is:

a) Same as physical quantity
b) Different from physical quantity
c) Unitless
d) Error has its own unit
Answer: c)

7. A student writes the length as 3.50 cm. Which instrument did he use?

a) Meter scale
b) Vernier caliper
c) Screw gauge (100 divisions)
d) Screw gauge (50 divisions)
Answer: b)

8. Pitch and divisions for least count 0.02 mm are:

a) 1 mm & 100
b) 0.5 mm & 50
c) 1 mm & 50
d) 0.5 mm & 100
Answer: c)

9. Difference between measured and true value is:

a) Absolute error
b) Relative error
c) Percentage error
d) None
Answer: a)

10. Absolute error is always:

a) Positive
b) Negative
c) Both a & b
d) None
Answer: c)

11. Error due to resolution of instrument is:

a) Parallax error
b) Systematic error
c) Random error
d) Least count error
Answer: d)

12. Smallest measurable value is called:

a) Least count
b) Parallax
c) Accuracy
d) Precision
Answer: a)

13. Which is not a systematic error?

a) Instrumental error
b) Imperfect technique
c) Personal error
d) None of these
Answer: c)

14. Accuracy indicates:

a) Precision
b) Closeness to true value
c) Error
d) None
Answer: b)

15. Error in radius = 1%. Error in sphere volume =

a) 1%
b) 5%
c) 3%
d) 8%
Answer: c)

16. For addition/subtraction, absolute error is:

a) Sum of absolute errors
b) Sum of relative errors
c) Either a or b
d) None
Answer: a)

17. Random error can be eliminated by:

a) Careful observation
b) Removing cause
c) Using multiple instruments
d) Taking large number of observations
Answer: d)

18. Ratio of mean absolute error to mean value:

a) Absolute error
b) Relative error
c) Percentage error
d) None
Answer: b)

19. Instrumental errors occur due to:

a) Imperfect design
b) Zero error
c) Both
d) None
Answer: c)

20. Systematic errors can be:

a) Positive only
b) Negative only
c) Either
d) None
Answer: c)

21. Which can measure length up to 10⁻⁵ m?

a) Meter scale
b) Vernier calipers
c) Spherometer
d) None
Answer: c)

22. 1 Parsec =

a) 3.1 × 10⁻¹⁶ m
b) 3.26 ly
c) 6.3 × 10⁴ AU
d) 1.496 × 10¹¹ m
Answer: b)

23. Universal time is based on:

a) Earth’s rotation
b) Earth’s orbit
c) Cesium atom
d) Quartz crystal
Answer: c)

24. Not a unit of time:

a) Microsecond
b) Leap year
c) Lunar month
d) Parallactic second
Answer: d)

25. Illuminance is measured in:

a) Lumen
b) Candela
c) Lux
d) Lux/m²
Answer: c)

26. Standard kilogram prototype in India is at:

a) National Physics Laboratory
b) Science Centre
c) CSIR
d) None
Answer: a)

27. Smallest unit:

a) Millimetre
b) Angstrom
c) Femti
d) Metre
Answer: c)

28. One yard in SI =

a) 1.9144 m
b) 0.9144 m
c) 0.09144 km
d) 1.0936 km
Answer: b)

29. Length cannot be measured by:

a) Femi
b) Debye
c) Micron
d) Light year
Answer: b)

30. Light year is:

a) Light emitted in one year
b) Time for light to reach Earth
c) Distance travelled by light in free space in one year
d) Time for Earth to orbit Sun
Answer: c)

31. 1 atomic mass unit is equal to:

a) 12× mass of C-12 atom
b) 1/12 of 12 atoms
c) 1/12 mass of one C-12 atom
d) 12× mass of 12 atoms
Answer: c)

32. Very large distances measured by:

a) Spectrograph
b) Oil drop method
c) Parallax
d) All
Answer: c)

33. 1° =

a) 17 rad
b) 17.45 × 10⁻² rad
c) 17.45 × 10⁻² rad
d) 1.745 × 10⁻² rad
Answer: d)

34. Second defined using Cesium 133 because:

a) Not affected by place
b) Not affected by time
c) Not affected by physical conditions
d) All
Answer: d)

35. Number of base SI units:

a) 4
b) 7
c) 3
d) 5
Answer: b)

36. System not based on M-L-T alone:

a) SI
b) MKS
c) CGS
d) FPS
Answer: a)

37. Most accurate measurement (mean = 5 cm):

a) 4.9 cm
b) 4.805 cm
c) 5.25 cm
d) 5.4 cm
Answer: a)

38. Most precise measurement:

a) 5.00 mm
b) 5.00 cm
c) 5.00 m
d) 5.00 km
Answer: a)

39. Pair NOT having same dimensional formula:

a) Work & torque
b) Angular momentum & Planck’s constant
c) Tension & surface tension
d) Impulse & momentum
Answer: c)

40. 2.745 & 2.735 rounded to 3 significant figures:

a) 2.75 & 2.74
b) 2.74 & 2.73
c) 2.75 & 2.73
d) 2.74 & 2.74
Answer: d)

Conclusion

Mastering significant figures, errors in measurement, and dimensional analysis offers a major advantage in NEET, JEE, and CUET physics. These topics enhance conceptual clarity and ensure accuracy during problem-solving. The 40 MCQs above combine conceptual depth with exam-oriented application, helping you memorise rules, avoid common mistakes, and build precision in experimental physics.