Measure The Thickness Of A Given Sheet Using Screw Gauge

Exams Prep Master

To measure the thickness of a particular sheet, we use different apparatus like Screw Gauge and Vernier Callipers. Compared to the vernier calliper, the screw gauge is a more precise tool. A screw gauge can be used to make more precise measurements up to 0.01 mm or 0.005 mm than the vernier callipers which measures length up to 0.1 mm. We'll look at how to use a screw gauge to determine the thickness of a sheet in this experiment.

Table of Content

Aim
Apparatus
Theory
Procedures
Observations
Calculations
End Result
Things to Remember
Sample Questions

Key Takeaways: Measure, thickness, sheet, screw gauge, anvil, spindle, zero error

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Aim

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Using a screw gauge, to determine the thickness of a given sheet.

Apparatus or Material Required

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A Screw Gauge.
A Magnifying glass.
A Paper sheet.

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Theory

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The Screw Gauge is a tool made out of a U-shaped metal Frame. It is used for measuring the dimensions of very small items down to 0.01 mm. One end of the frame has a hollow cylinder attached to it. Grooves are carved into the inside surface of the cylinder to allow a screw to pass through. A millimetre scale called the Main scale or Pitch Scale is graduated on the cylinder parallel to the axis of the screw. A Sleeve is fastened to one end of the screw. The Rotating scale or Head Scale divides the head of the sleeve into 100 segments. The screw's other end has a flat surface called Spindle. A stud or Anvil is attached to the opposite end of the frame, exactly opposite the screw tip. The screw Mild head or Thimble has a Ratchet arrangement (safety mechanism) to prevent the operator from applying excessive pressure.

Screw Gauge Operation Principle

The screw gauge operates on the screw concept. The distance travelled by the tip of a screw when it is rotated in a nut is exactly proportional to the number of revolutions.

Pitch of the Screw Gauge

A screw's pitch is the distance travelled along its axis by the screw in one full rotation of its head.

Pitch= (Distance travelled by the screw) / (No. of Full rotation taken)

Screw Gauge and its Least Count

When rotating the circular scale by one division, the distance travelled down the axis by a screw has the smallest count.

Turning the tip of the screw gauge by one division of the head scale yields the least count (LC).

Least Count = (Pitch) / (Total number of divisions in the circular scale) = (1 mm)/(100) = 0.01 mm.

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Screw Gauge Zero Error and Zero Correction

Before conducting the experiment it is compulsory to find zero error in the apparatus. The zero error can be found by completely rotating the screw until it strikes the anvil. If the plane surface of the screw and the opposite plane stud on the frame come into contact and the zero of the head scale aligns with the pitch scale axis, there is no zero error.

These are some of the readings we find when we find zero error:

There is no zero error when the screw's plane surface and the opposite plane stud on the frame make contact, and the head scale's zero aligns with the pitch scale axis.
The zero error is found positive if the zero of the head scale sits below the pitch scale axis. If, for example, the 5th division of the head scale coincides with the axis of the pitch scale, the zero error is positive.
The zero error is found negative if the zero of the head scale is above the pitch scale axis. For example, the fifth division corresponds to the pitch scale axis.

Procedures

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Determine the value of a single linear scale division (L.S.D.).
Determine the screw gauge's pitch and least count and record it step by step
Make contact between Spindle and Anvil and calculate the zero error. Repeat it three times and record the results. Record nil for zero error if you don't find zero error.
Separate the two faces from each other. Place the sheets lengthwise over the anvil and use the ratchet head to move the spindle towards the anvil. When the head rotates (slips) without moving the screw, come to a halt.
Count the number of divisions of the linear scale that are visible and uncovered by the cap's edge. The reading (IV) is referred to as a linear scale reading (L.S.R.).
Take note of the number (n) of the divisions of the circular scale that lies over the reference line.
Repeat steps 4,5,6 for 5 different spots distributed evenly over the sheet's surface. Make a tabular record of your observations.
Determine the total reading and apply the zero correction in each case.
Calculate the average of different thickness values.

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Observations

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Determination of the Screw Gauge's Least Count. 1 mm Equals 1 L.S.D. The number of full revolutions delivered to the screw is equal to four. 4 mm is the distance moved by the screw. As a result, pitch p = 4 mm/4 = 1 mm. The number of divisions on a circular scale equals 100.

As a result, the lowest count is =1 mm/100 = 0.01 mm = 0.001 cm.

Zero Error. (i)…….mm,(ii)…… mm, (iii)…….mm.

Mean zero error (e) =……..mm

Mean zero correction (c) = – e =……mm.

NO. OF OBSERVATIONS	LINER SCALE READING(mm)	Circular scale reading	Total READING
	No. of divisions on reference line (n)	Value N x l.c (mm)	OBSERVED T₀ =N+n x L.C (mm)	CORRECTED t= t₀ + c (mm)
1. 2. 3. 4.				t₁ = t₂ = t₃ = t₄ =

Calculations

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Determine the value of t for each observation and record the observed value t0 in column (4a).
Fill in the column with the revised value of t. (4b).
Determine the mean of the t values entered in column (4b).

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End Result

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The provided sheet has a thickness of........ mm.3.

Safety Measures

To minimise unnecessary pressure, always rotate the screw with ratchet R rather than cap K.
The screw should slide freely without friction.
The zero correction, with a suitable sign, should be properly documented and algebraically added.
To avoid screw back-lash, the screw should be moved in the same direction for the same set of observations.
Readings should be taken at least five times at different places of the sheet, evenly spaced.
Parallax errors should be avoided.

Chances of Error

Uneven sheet
Friction may exist in the screw.
Back-lash inaccuracy in the screw gauge is possible.
Circular scale divisions may or may not be the same size.

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Things to Remember

To measure the thickness of a particular sheet, we use specific apparatus like Screw Gauge as it is a more precise tool.
Apparatus used in the experiment are Screw Gauge, Magnifying glass, Paper sheet.
A screw gauge is made up of a "U" shaped metallic component that is mounted to one end of a hollow cylindrical tube. Inside the hollow tube is an evenly threaded nut.
The essential components of a screw gauge are: Frame, Anvil, Spindle, Sleeve, Thimble, Ratchet, Screw.
Before conducting the experiment it is compulsory to find zero error in the apparatus. Least count of screw gauge is = (1 mm)/(100) = 0.01 mm
This experiment comprises various steps like theory, procedure, observations, calculations, precautions and end results.
The mean thickness of the sheet can be calculated by t= t₁+t₂+t₃+t₄/4, where t is the observed value.

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Sample Questions

Ques. Which of the following measurements for thickness is possible using a screw gauge with a pitch of 0.1 cm and a division of 100 on a circular scale? (2 marks)

Ans. The most exact instrument is the one with the lowest count.

Now, Screw gauge least count '="Pitch"/"No. of divisions on circular scale"' '=1/100mm=1/1000cm=0.01cm'

Ques. The pitch of a screw gauge is 0.1 cm and it contains 50 circular scale divisions. When measuring the thickness of a plate using this, the main scale reading is 0.2 cm and the circular scale reading is 35. What is the plate's thickness? (2 marks)

Ans. The thickness of the plate = main scale reading +circular scale reading x least count

The screw gauge's least count (c) is '(0.1)/(50)' = 0.002 cm.

As a result, the plate thickness is t = 0.2 cm + 35 'xx '0.002 cm = 0.27 cm.

Ques. A screw gauge has a pitch of 0.5 cm and 100 circular scale divisions. When measuring the thickness of a plate using this, the main scale reading is 1.5 cm and the circular scale reading is 69. What is the plate's thickness? (2 marks)

Ans. The thickness of the plate = main scale reading +circular scale reading x least count

Least Count =pitch /no.of circular scale division

As a result, the plate thickness is t = 1.5mm + 69 x0.5/100mm = 1.845mm.

Ques. What do you mean by the pitch of a screw? (1 mark)

Ans. The distance pitch of the screw is between the two nearest threads along the axis of the screw.

Ques. What is the least count of the screw gauge? (1 mark)

Ans. The least count of the screw gauge is 0.001 cm.

Ques. What do you mean by the zero error of a screw gauge? (3 marks)

Ans. The error arises when the zero of the circular scale does not coincide with the zero of the main scale upon joining the two studs.

Some of the readings that we find zero error:

There is no zero error when the screw's plane surface and the opposite plane stud on the frame make contact, and the head scale's zero aligns with the pitch scale axis.
The zero error is found positive if the zero of the head scale sits below the pitch scale axis. If, for example, the 5th division of the head scale coincides with the axis of the pitch scale, the zero error is positive.
The zero error is found negative if the zero of the head scale is above the pitch scale axis. For example, the fifth division corresponds to the pitch scale axis.

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Measure The Thickness Of A Given Sheet Using Screw Gauge

Aim

Apparatus or Material Required

Theory

Screw Gauge Operation Principle

Pitch of the Screw Gauge

Screw Gauge and its Least Count

Screw Gauge Zero Error and Zero Correction

Procedures

Observations

Calculations

End Result

Safety Measures

Chances of Error

Things to Remember

Sample Questions

CBSE CLASS XII Related Questions

1.
Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

4.
Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

5.
Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

6.
What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?

Comments

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Measure The Thickness Of A Given Sheet Using Screw Gauge

Aim

Apparatus or Material Required

Theory

Screw Gauge Operation Principle

Pitch of the Screw Gauge

Screw Gauge and its Least Count

Screw Gauge Zero Error and Zero Correction

Procedures

Observations

Calculations

End Result

Safety Measures

Chances of Error

Things to Remember

Sample Questions

CBSE CLASS XII Related Questions

1.Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

4. Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

5.Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

6.What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?

Comments

SUBSCRIBE TO OUR NEWS LETTER

1.
Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

4.
Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.

5.
Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

6.
What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?