Can you measure the diameter of your hair by screw gauge?

Activity A

Índice Show

Aim of the Practical
What is the Apparatus Requirement in the Experiment?
Apparatus Description
Pitch of the Screw Gauge
Least Count of the Screw Gauge
Zero Error and Zero Correction
Experiment Observation Table
Calculation
Final Result
Sources of Error
How will you measure the diameter of a hair?
What instrument can be used to measure a diameter of hair?
Can a micrometer screw gauge measure hair?
What can measure the thickness of hair?

Aim:

· To measure the thickness of your hair using micrometer screw gauge

Apparatus:

· Micrometer screw gauge

Procedure and Results:

a. Observe the micrometer screw gauge. What do one division on the main scale and the rotating scale represent?

1 division on main scale = 1 mm

1 division on rotating scale = 0.01 mm

b. Close the anvil and spindle. Is there any zero error for your micrometer screw gauge? If yes, what is the value of the zero error?

There is / is no zero error for the micrometer screw gauge.

The value of zero error is 0 mm.

c. Measure the thickness of your hair at 3 different points along the length of the hair, and record your measurements, h1, h2 and h3 for each point, in the table below (make sure you account for zero error, if any). Calculate the average thickness of your hair, < h >, correcting your answer to the same number of decimal places as your measurement.

	h1	h2	h3	< h >
Measured value / mm	0.05	0.04	0.06	0.05
Corrected value / mm	NIL	NIL	NIL	NIL
Corrected value / cm	NIL	NIL	NIL	NIL

My ruler has a diameter/thickness of 0.94mm!

Activity B

Do a comparison of ruler, vernier calipers and micrometer screw gauge in the table below.

	Precision	Advantages	Disadvantages	How to minimise errors when using this instrument?
Ruler	1mm	Is useful for measuring straight objects	-Not fully accurate: When the object has a length of between 1mm and the next, it is impossible for it to have a precise reading - Usually goes up to about an average of 30cm which is neither here nor there; cannot measure short lengths; cannot measure long lengths	Try to keep the object as flat as possible.
Vernier calipers	0.01mm	- Can measure the width—internal or external quite accurately - Can also measure a certain degree of depth	- Has a tendency of zero error	Always calculate zero error first
Micrometer screw gauge	0.01mm	Can measure very accurately the width of the least wide objects—such as a strand of hair	- Has a tendency of zero error - Can only measure limited widths - Cannot measure lengths/breadths etc..; only widths of objects	Always calculate zero error first

A screw gauge is a tool for precisely measuring the diameter of a thin wire or the thickness of a metal sheet. You can usually measure length precisely up to 0.1 mm with Vernier Calipers. A screw gauge can be used to make more precise length measurements of up to 0.01 mm or 0.005 mm.

As a result, a Screw Gauge is a more precise instrument than Vernier Calipers. A screw has threads on it. Any two successive threads are separated by the same amount of space. By twisting the screw anticlockwise or clockwise in its nut, it can be moved backwards or forward.

We all know that Vernier calipers are one of the precision instruments that can actually measure with an accuracy of up to 0.1 mm. At the same time, higher accuracy can be attained using Screw Gauge. A Screw Gauge can take measurements up to 0.01 mm to even 0.005 mm. The sole idea behind this experiment is to find how to measure the thickness of a sheet of paper using a screw gauge.

Aim of the Practical

The aim of the experiment is to measure the thickness of a given sheet using a screw gauge.

What is the Apparatus Requirement in the Experiment?

Screw gauge
Sheet
Magnifying Lens

Apparatus Description

A screw gauge is made up of a U-shaped frame with a screwed spindle connected to a thimble. A scale graduated in mm is carved parallel to the thimble's axis. Pitch scale is the term for this. A sleeve is affixed to the screw's head.

A ratchet on the screw head prevents the screw from being overtightened. A circular scale known as the head scale is found on the thimble and is divided into 50 or 100 equal sections. The sleeve moves around the pitch scale when the screw is turned.

The anvil is a stud with a plane end surface that is positioned precisely opposite the screw tip on the 'U' frame. When the screw's tip makes contact with the anvil, the head scale's zero normally corresponds with the pitch scale's zero.

Theory

Screw gauge is one of the precision instruments that can be used to accurately measure the thickness of a paper, or even the diameter of a thin wire. The structure of a screw gauge consists of a U-shaped frame along with a screw spindle that is attached to the thimble. In a screw gauge, mm scales are engraved, running parallel to that of the thimble.

(Image will be uploaded soon)

The head section of the screw gauge consists of a ratchet that restricts the over-tightening of the screw. Within the thimble section, it consists of a circular scale that is divided into 50 or 100 equal parts. It is also termed as a head screw, which moves over the pitch scale while operating.

The anvil, which is the stud with a plane end surface, forms the U shaped frame. It can be found on the opposite side to the tip of the screw. You will find the zero of the head scale coinciding with that of the pitch scale. This occurs when the tip of the screw comes in contact with that of an anvil.

Pitch of the Screw Gauge

The pitch of the screw gauge can be defined as the distance traveled by the spindle per rotation. The pitch of the screw gauge can be determined by the distances traveled by the screw, divided by the total number of rotations.

The formula for pitch is given by:

Pitch of the Screw = \[\frac{\text{(Distance travelled by the screw)}}{\text{(Number of Full rotation taken)}}\]…………. (1)

Principle

The screw's linear distance traveled is proportional to the spin applied to it. The smallest distance that the instrument can reliably measure is the linear distance moved by the screw when rotated by one division of the circular scale. It's known as the instrument's least count.

Least Count of the Screw Gauge

When the tip of the screw gauge is turned by one division of the head scale, the least count (LC) is taken.

The formula for calculating least count is given by:

Least Count =\[\frac{\text{(Pitch)}}{\text{(Total number of divisions in the circular scale)}}\] …………. (2)

Zero Error and Zero Correction

By looking at the screw gauge image, one needs to consider the zero error in the calculation. The zero error can be calculated by completely rotating the screw until it touches the anvil. Make sure that the edge of the cap is located at the zero marking. The screw gauge needs to be kept vertical so that its zero is facing downward.

By attaining the same position, you can come across three circumstances:

The zero marks from the circular scale align with that of the reference scale. Here, no scope of zero error or zero correction can be found.
The zero marks from the circular scale actually remain above that of the reference scale. Here, the zero error is considered positive, while the zero correction is negative.
The zero marks from the circular scale are actually below the reference line. Here, the zero error is considered negative, while the zero correction is positive.

Procedure

In order to properly conduct the experiment, make sure to go through the following procedure carefully:

Determine the screw gauge's pitch (1) and least count (2) using the above equations.
To determine the zero error, make contact between the anvil and the screw. Perform it three times and keep track of the results. If no zero errors occur, the value 'zero error nil' is recorded.
Using the ratchet head, move the screw away from the anvil, insert the lead shot, and then return the screw to its original position. Stop then and there if the ratchet slips without moving the screw.
Count the number of pitch scale divisions visible and uncovered by the cap's edge. The pitch scale reading (PSR) is denoted by the letter N.
Count the number (n) of circular scale divisions that cross the reference line.
To measure the diameter perpendicularly, repeat steps 4 and 5 after rotating the lead shot by 900 degrees. Fill in the blanks with your observations in the tabular column.
Calculate the total reading by using the equation gives as:

t = PSR + corrected HSR = N+(n x L.C) and apply zero correction in each case.

Find the mean of the various values.
Make sure to insert the sheets in between the studs of the screw gauge. Take the calculation of thickness from five different positions.
Make sure to calculate the average thickness, while determining the correct thickness by zero error.

Experiment Observation Table

Serial Number	Linear scale reading M (mm)	Circular scale reading n	Thickness t = N + n × L.C. (mm)
1
2
3
4
5

Calculation

Least count _____ mm
Zero Error _____ mm
Mean thickness of the paper _____ mm
Mean corrected thickness of the paper
Thickness observed through screw gauge – Zero error _____ mm

Final Result

As a result, the thickness of the given sheet of paper comes out is _____ mm

Sources of Error

The thickness of the sheet may not be consistent.
Although backlash-related errors can be reduced, they cannot be entirely eliminated.

How will you measure the diameter of a hair?

If a fine wire or hair is placed in the beam of a small laser, a diffraction pattern is produced. We can determine the diameter of the hair by mea- suring the spacings of the maxima or minima.

What instrument can be used to measure a diameter of hair?

One can think of several methods how to do it (micrometer screw gauge can be used for example). We are going to measure the diameter of a human hair by diffraction of a laser beam. The thickness of the human hair is just a bit more than a magnitude of the laser light used.

Can a micrometer screw gauge measure hair?

Hair diameters range from 15 microns for very fine hair up to 140 microns for very course hair, where the hair diameter of an average person is around 70 microns. With this, stand alone, accurate and high resolution micrometer, you can easily and quickly measure hair diameters and better predict your final result.

What can measure the thickness of hair?

The most accurate — but least practical — way to measure your hair density is by counting the individual strands in a 1-inch by 1-inch section of your scalp. Researchers commonly use an imaging technique called trichoscopy in lab settings to achieve this.