Measurement | Practical No 02 - Usage of the micrometer screwgaugae | A/L Physics Practical

DP Education - A/L සිංහල මාධ්‍යය・2 minutes read

A micrometer screw gauge provides high accuracy in length measurements with a least count of 0.01 millimeters, suited for precise measurements of small objects; meanwhile, vernier calipers are better for measuring internal diameters and depths. To ensure accurate readings, align the circular scale zero with the main scale, address zero errors, and rotate objects to obtain multiple readings for averaging and improved precision.

Insights

Vernier calipers offer greater accuracy than meter rulers due to their 0.1 millimeter least count, enabling measurements below 1 millimeter.
Micrometer screw gauges provide enhanced accuracy in length measurements compared to Vernier calipers, with a 0.01 millimeter least count.
To ensure precise measurements with a micrometer screw gauge, align the circular scale with the main scale zero to eliminate zero errors, rotate the thimble to secure the object, and average multiple readings for accuracy.

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Recent questions

How does a micrometer screw gauge differ from a Vernier caliper?
Micrometer screw gauge has 0.01mm least count.

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Summary

00:00

Precision Measurement Tools: Vernier vs. Micrometer

Vernier caliper offers better accuracy than a meter ruler due to its 0.1 millimeter least count, allowing measurements below 1 millimeter.
A manufacturer's claim of 0.18 millimeter wire diameter cannot be verified using a Vernier caliper with a 0.1 millimeter least count.
Micrometer screw gauge boasts a 0.01 millimeter least count, enhancing accuracy in length measurements compared to Vernier calipers.
Micrometer screw gauge lacks internal jaws like Vernier calipers, limiting its ability to measure internal diameters.
Micrometer screw gauge can measure external diameters of objects with precision, akin to Vernier calipers' external jaws.
Components of a micrometer screw gauge include an anvil for object placement and a spindle moved by a thimble head for measurement.
To ensure accurate measurements, a tick sound indicates when the spindle and anvil are in contact, preventing object deformation.
The circular scale on the thimble of a micrometer screw gauge determines its least count, calculated by divisions on the scale and main scale movement.
Practical applications of a micrometer screw gauge involve measuring the thickness of a microscope slide, steel ball diameter, and paper thickness.
Prior to measurements, ascertain the micrometer screw gauge's least count, eliminate zero errors by aligning circular scale and main scale zeros, and follow a sequential learning approach for experiments to build cumulative knowledge.

18:39

Precision Measurement with Micrometer Screw Gauge

The zero of the main scale and one of the circular scales must align, with the circular scale's zero on the main line to indicate no zero error.
The circular scale numbers progress from one to 99 in a 100-division scale, moving anti-clockwise to open the gap between the anvil and spindle.
To adjust for zero error, rotate the thimble anti-clockwise to close the gap and align the circular scale zero with the main scale zero.
Positive zero error occurs when the circular scale surpasses the main scale zero, while negative zero error happens when the circular scale falls short of the main scale zero.
Calculate the error by subtracting the actual reading from the zero error value, adjusting for positive or negative error accordingly.
Obtain measurements using the micrometer screw gauge by placing the object between the anvil and spindle, rotating the thimble to secure it, and reading the main and circular scales.
Measure the diameter of a thin wire by rotating it 90 degrees for multiple readings and averaging them for accuracy.
Determine the thickness of a microscope slide by obtaining readings at three different points and averaging them.
Measure the radius of a steel ball by taking readings for three diameters perpendicular to each other and calculating the average.
Utilize the micrometer screw gauge to ensure precise measurements for small objects, minimizing errors and achieving high accuracy in experimental results.

37:58

"Precision Measurement with Micrometer Screw Gauge"

An anvil and spindle are fixed parts of a micrometer screw gauge, with the spindle being the moving part controlled by the thimble head.
The main scale of the micrometer screw gauge measures in increments of 0.5 millimeters, with additional markings for half-millimeter measurements.
A circular vernier scale on the micrometer screw gauge aligns with the main scale, with 50 sections indicating a movement of 0.5 millimeters per full rotation.
The least count of the micrometer screw gauge is calculated as 0.01 millimeters by dividing the pitch of 0.5 millimeters by the 50 sections on the circular scale.
Zero error in the micrometer screw gauge is determined by aligning the circular scale's zero with the main scale's horizontal line, with positive and negative errors indicated by misalignment.
Positive zero error is when the circular scale is to the right of zero, while negative zero error occurs when it passes zero, with adjustments needed for accurate measurements.
To measure an object's diameter using the micrometer screw gauge, the anvil and spindle are opened, the object is placed between them, and the gap is closed until a ticking sound is heard.
The diameter is then read by noting the main scale measurement and the circular scale's alignment, with multiple measurements taken at different points for accuracy.
Rotating the object by 90 degrees between measurements helps account for any slight variations in diameter, ensuring precise readings.
Averaging the measurements taken at different points provides a more accurate representation of the object's diameter.

56:57

Precision Measurement Techniques for Accurate Results

When calculating averages with an apparatus having a least count of 0.01, round the average to the second decimal point for accuracy.
To measure the thickness of a glass slide, place it between the anvil and spindle, align the readings, and record the measurement in millimeters.
Use a micrometer screw gauge to measure the diameter of a steel ball by aligning the main and circular scales to obtain precise readings.
The micrometer screw gauge provides accurate measurements due to its least count of 0.01 millimeters, ensuring high precision for smaller lengths.
To measure the diameter of a thin wire accurately, use a micrometer screw gauge for its 0.01 millimeter precision, crucial for small measurements.
Obtain the diameter of a sonometer wire by measuring it at various points perpendicular to the wire, averaging the measurements for accuracy.
While a micrometer screw gauge can measure external diameters precisely, vernier calipers are suitable for measuring internal diameters and depths.
Choose a spring balance with a range close to the expected mass for high sensitivity, such as a 150-gram balance for a 100-gram metal ball.
Variations in diameter measurements of a metal ball may occur due to its non-uniform shape, leading to different readings at various points.
Consider using a vernier caliper for diameter measurements with fluctuations in the second decimal of centimeters, as it provides sufficient accuracy for such variations.

01:17:58

Volume Measurement Techniques and Micrometer Screw Gauge

The mass of the hook is assumed to be 1/50th of the full mass, so the diameter is calculated as 49m/50 divided by the volume formula 4/3πr³.
An alternative method to find the volume of a ball involves using a measuring cylinder, filling it with water to a certain level, dropping the ball in, and measuring the change in water level.
Advantages of the water displacement method over measuring the diameter include accurate volume measurement for non-perfect spheres and accounting for cracks in the ball.
Parts of a micrometer screw gauge include the sleeve (a), thimble scale (b), thimble (c), and thimble head or ratchet (d).
The least count of the micrometer screw gauge is 0.01 millimeters, with a scale reading for the ball's diameter at 6.48 millimeters.
Adjusting the micrometer screw gauge to correct zero error results in a negative error of 0.04 millimeters, leading to a corrected diameter reading of 6.52 millimeters.
The fractional error of the measurement can be half the least count or the least count itself, depending on the precision needed.
To avoid over-pressing an object with a micrometer screw gauge, rotate using the thimble head or ratchet to produce a ticking sound when the spindle touches the object.
For measuring a wire length, use a meter ruler; for a wire diameter, a micrometer screw gauge; for a disk diameter, a vernier caliper; and for disk thickness, a micrometer screw gauge.
To obtain a better value for the disk thickness, measure at multiple points and average the results; for a thin polythene sheet, fold it into multiple layers and measure the thickness to find the average.

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