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NEET Physics: least count Practice Questions

15 free multiple-choice questions on least count (Physics and Measurement) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. A vernier calliper has a least count of 0.01 cm. What does this value signify?

    • AThe instrument has a reading error of 0.01 cm.
    • BThe instrument can measure lengths up to 1 cm.
    • CThe smallest measurement that the instrument can measure accurately.
    • DThe instrument is designed to measure only lengths greater than 0.01 cm.
    Show answer & explanation

    Correct answer: C — The smallest measurement that the instrument can measure accurately.

    The least count defines the smallest measurement that the instrument can measure accurately.

  2. Q2. Which of the following statements is always true regarding the least count of a measuring instrument?

    • AThe least count represents the smallest measurement that can be accurately recorded by the instrument.
    • BThe least count is always the smallest division on the instrument scale.
    • CThe least count is determined by the precision of the measuring device itself.
    • DThe least count is inversely proportional to the accuracy of the measurement.
    Show answer & explanation

    Correct answer: A — The least count represents the smallest measurement that can be accurately recorded by the instrument.

    The least count is the smallest measurement that can be measured or recorded by a particular measuring instrument. It defines the limit of precision for that instrument.

  3. Q3. The least count of a screw gauge is generally given by the pitch of the screw. This indicates the instrument's ability to measure which quantity?

    • ATime
    • BTemperature
    • CMass
    • DLength
    Show answer & explanation

    Correct answer: D — Length

    Screw gauges are used primarily for measuring linear dimensions (length), and their least count is related to the pitch of the screw used.

  4. Q4. If a measuring scale has divisions of 5 mm, what is the smallest distance that can be measured accurately?

    • A1 mm
    • B0.5 mm
    • C10 mm
    • D5 mm
    Show answer & explanation

    Correct answer: D — 5 mm

    The smallest distance measurable is equal to the smallest division marked on the scale, which is 5 mm.

  5. Q5. If an instrument has a smallest division of 0.1 cm, what is the least count of the instrument?

    • A1 cm
    • B0.01 cm
    • C0.1 cm
    • D10 cm
    Show answer & explanation

    Correct answer: C — 0.1 cm

    The least count of an instrument is the smallest measurement it can measure. If the smallest division on the scale is 0.1 cm, then the least count is 0.1 cm.

  6. Q6. If an instrument measures quantities in units of 10⁻³ meter, what is the least count when the measurement is taken to be 5.0 × 10⁻³ meter?

    • A5.0 × 10⁻³ meter
    • B10⁻³ meter
    • C10⁻⁶ meter
    • D5.0 meter
    Show answer & explanation

    Correct answer: B — 10⁻³ meter

    The least count of the instrument dictates the smallest measurable increment, which is 10⁻³ meter. The actual reading 5.0 × 10⁻³ meter is a specific value within that scale.

  7. Q7. What is the least count when a measuring scale has markings every 5 mm?

    • A1 mm
    • B0.5 mm
    • C0.1 mm
    • D5 mm
    Show answer & explanation

    Correct answer: A — 1 mm

    The least count is determined by the smallest division on the scale. If the smallest division is 5 mm, the least count is 5 mm.

  8. Q8. A student measures the length of a pencil using a ruler marked in millimeters. If the smallest division on the ruler is 1 mm, what is the least count of the measurement in millimeters?

    • A0.1 mm
    • B100 mm
    • C1 mm
    • D10 mm
    Show answer & explanation

    Correct answer: C — 1 mm

    The least count of a measurement is determined by the smallest division marked on the measuring scale. Since the smallest division is 1 mm, the least count is 1 mm.

  9. Q9. If a thermometer has markings every 1° C, what is the least count of this thermometer?

    • A0.1° C
    • B0.01° C
    • C1° C
    • D0.5° C
    Show answer & explanation

    Correct answer: C — 1° C

    The least count is the smallest interval marked on the scale, which in this case is 1° C.

  10. Q10. What is the least count of a measuring instrument?

    • AThe smallest measurement that can be measured by the instrument.
    • BThe reading of the zero mark.
    • CThe total range of the instrument.
    • DThe value of the smallest division on the main scale.
    Show answer & explanation

    Correct answer: A — The smallest measurement that can be measured by the instrument.

    The least count is the smallest measurement that can be accurately measured by a particular instrument.

  11. Q11. Which of the following statements correctly describes the least count?

    • AIt represents the exact value of the physical quantity being measured.
    • BIt determines the error in the reading only.
    • CIt is the smallest measurable value that the instrument can indicate.
    • DIt defines the maximum reading capacity of the instrument.
    Show answer & explanation

    Correct answer: C — It is the smallest measurable value that the instrument can indicate.

    The least count is the smallest measurable value that the instrument is capable of indicating.

  12. Q12. If a physical quantity is measured using an instrument having a least count of 0.1 cm, what is the minimum error in the measurement?

    • A0.05 cm
    • B0.2 cm
    • C1 cm
    • D0.1 cm
    Show answer & explanation

    Correct answer: A — 0.05 cm

    The least count represents the smallest measurable increment. Therefore, the minimum error or uncertainty in the measurement is equal to the least count of the instrument.

  13. Q13. If a scale has markings in increments of 1 mm, what is the smallest measurable quantity (least count) of this scale?

    • A1 cm
    • B10 mm
    • C1 mm
    • D0.1 mm
    Show answer & explanation

    Correct answer: C — 1 mm

    The least count is the smallest interval between two consecutive markings. If the markings are in increments of 1 mm, the least count is 1 mm.

  14. Q14. The precision of a measuring instrument is directly related to its least count. Which of the following statements correctly describes the relationship?

    • APrecision is defined by the total number of divisions on the scale.
    • BSmaller least count implies lower precision.
    • CGreater least count implies greater precision.
    • DPrecision is independent of the least count.
    Show answer & explanation

    Correct answer: B — Smaller least count implies lower precision.

    A smaller least count means the instrument can measure smaller values, indicating higher precision. Therefore, a smaller least count implies higher precision.

  15. Q15. If a student measures a length using a ruler marked only in whole centimeters, what is the smallest unit of length that can be accurately determined?

    • A100 mm
    • B1 cm
    • C10 mm
    • D0.5 cm
    Show answer & explanation

    Correct answer: C — 10 mm

    Since the ruler only marks whole centimeters, the smallest unit it can reliably measure is the smallest marking, which is 1 cm or 10 mm.

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