Experimental Skills for NEET 25 are key to scoring marks in Physics! At least 1-2 questions from this topic can appear in the exam. Since these questions are relatively easy, you can score well by practicing and attempting them confidently.
Vernier calipers
A Vernier caliper is a precise tool used to measure the internal and external sizes of objects and the depth of containers. It has two scales: a fixed main scale and a movable Vernier scale. Together, these scales provide highly accurate measurements. It was invented in 1631 by French scientist Pierre Vernier.
The main parts of a vernier Calliper are:
- Main Scale: The main scale is a graduated scale that is used to measure the overall length of an object.
- Vernier Scale: The vernier scale is a second scale that is used to measure small increments of length.
- Fixed Jaw: The fixed jaw is the stationary jaw of the vernier Calliper. It is used to measure the outside of an object.
- Movable Jaw: The movable jaw is the movable jaw of the vernier Calliper. It is used to measure the inside of an object.
- Zero adjustment screw: The zero adjustment screw is used to ensure that the Vernier Calliper is properly zeroed before taking a measurement.
- Locking Screw: The locking screw is used to secure the movable jaw in place after taking a measurement.
- Lower Jaws: The jaws of the vernier caliper, a key feature, include a fixed jaw connected to the main scale and a movable jaw connected to the vernier scale. Designed for a secure grip, the lower jaw primarily measures outer dimensions like diameter, width, and length.
- Upper Jaws: Smaller than the lower jaws, the upper jaws, attached to the top of the vernier scale, include a fixed and a movable part. Primarily used for measuring inner dimensions, the upper jaws are opened to touch the edges of objects like hollow pipes and jars for accurate readings.
- Depth Screw: Measure jar depths easily with the depth rod at the end of the main scale. Place the scale’s edge on the object’s top surface, open the jaws until the depth rod extends to the bottom for an accurate reading.
- Thumb Screw: The thumbscrew, at the bottom of the vernier scale, ensures a secure grip for easy sliding of the jaws.
- Lock Screw: The lock screw’s primary role is to secure the jaws in place once the object is firmly held, facilitating accurate readings.
How to Use a Vernier Calliper
To use a vernier Calliper, follow these steps:
Step 1: Make sure that the vernier Calliper is properly zeroed. To do this, loosen the locking screw and adjust the movable jaw until the zero mark on the vernier scale aligns with the zero mark on the main scale.
Step 2: Place the object to be measured between the fixed and movable jaws.
Step 3: Tighten the locking screw to secure the movable jaw in place.
Step 4: Read the measurement from the main scale and the vernier scale. The main scale will give you the overall length of the object, while the vernier scale will give you the small increments of length.
Vernier Constant or Least Count
The difference between one scale division and one Vernier division is called Vernier constant or the least count of the Vernier Calliper. Here, it is important to note that the divisions on the vernier scale are slightly smaller than the divisions on the main scale.
VC = 1 MSD – 1 VSD
If there are n divisions on the Vernier Scale then if they coincide with (n-1) division on the main scale, now the least count of the Vernier Scale is,
There fore Least Count can be expressed as
\[ \begin{array}{l} LC = 1\,M.S.D\, – \,\dfrac{{\left( {n – 1} \right)}}{n}\,M.S.D \\ \Rightarrow \,LC = \dfrac{1}{n}\,M.S.D \\ \end{array} \]Where,
- VC is Vernier Constant
- MSD is Main Scale Division
- VSD is Vernier Scale Division
- LC is Least Count
For example, if the main scale has divisions of 1 mm and the vernier scale has 10 divisions, then the least count of the vernier Calliper is 0.1 mm.
\[ \,LC = \dfrac{1}{{10}}\,M.S.D = \,\\\dfrac{1}{{10}}\,1\;mm\; = \;0.1\;mm \]What is Zero Error?
We define zero error as the condition in which the measuring device registers a reading when there should not be any reading. There are two types of zero errors that are,
- Positive Zero Error
- Negative Error
Positive Zero Error
In the case of the positive zero error, the reading is positive and away from the actual reading of 0.00 mm. That is if the reading is 0.06 mm in this case, then the zero error is +0.06 mm.
Negative Zero Error
In the case of the negative zero error, the reading is negative and away from the actual reading of 0.00 mm. That is if the reading is 0.06 mm in this case, then the zero error is -0.06 mm.
Zero Error in Vernier Callipers
Zero error in vernier Callipers is the error that occurs when the jaws of the Calliper are closed and the zero mark on the vernier scale does not coincide with the zero mark on the main scale. Zero error can be either positive or negative. Positive zero error means that the vernier scale is ahead of the main scale, while negative zero error means that the vernier scale is behind the main scale.
In the case of the Vernier Calliper, the zero error is calculated using the formula,
Actual Reading = Main Scale + Vernier Scale
Applications of Vernier Callipers
Vernier Callipers are used in a variety of applications, including:
- Manufacturing: Vernier Callipers are used to measure the dimensions of parts in manufacturing.
- Engineering: Vernier Callipers are used to measure the dimensions of structures and components in engineering.
- Science: Vernier Callipers are used to measure the dimensions of objects in science experiments.
- Construction: Vernier Callipers are used to measure the dimensions of materials in construction.
Safety Precautions
When using a vernier Calliper, it is important to take the following safety precautions:
- Always use a vernier Calliper that is in good condition.
- Do not use a vernier Calliper to measure objects that are too large or too small for the instrument.
- Do not use a vernier Calliper to measure objects that are sharp or pointed.
- Do not use a vernier Calliper to measure objects that are hot or cold.
- Store a vernier Calliper in a safe place when not in use.
How to Read Vernier Calliper?
To ensure accurate measurements, begin by verifying the alignment of the main and vernier scales with nothing in between. When both scales read zero, zero error is eliminated. Introduce a ball between the vernier scale jaws, aligning the 0 mark on the vernier scale with the main scale to obtain the main scale reading. Identify the point on the vernier scale aligned with the main scale for the vernier scale reading. Note that readings often involve decimals, with the number before the decimal indicating the main scale reading and the number after the decimal representing the vernier scale reading.