Which instrument can be used for angular measurement. Explain its working principal.
The correct answer and explanation is:
Correct Answer: Vernier Bevel Protractor
A Vernier bevel protractor is one of the most commonly used instruments for angular measurement in mechanical and engineering fields. It is known for its precision in measuring angles with high accuracy.
Working Principle:
The working principle of the vernier bevel protractor is based on the vernier scale principle. This principle allows the instrument to measure small differences in angle by comparing the alignment of markings on two scales: the main scale and the vernier scale. The smallest angle that can be measured accurately depends on the least count of the vernier scale.
Explanation (300 Words):
The vernier bevel protractor consists of a base blade, a circular graduated dial, and a vernier scale that allows fine readings. The base blade is fixed to the body of the protractor, and the dial can rotate freely. The object whose angle is to be measured is placed such that one edge aligns with the base blade and the other with the adjustable blade or arm. The circular scale is graduated in degrees, typically from 0 to 360.
The vernier scale is mounted on the dial and helps read finer divisions of angles. When the object is aligned between the two blades, the user reads the angle from where the zero of the vernier scale lines up with the main scale. Then, by observing which vernier division coincides with a division on the main scale, the user can find the precise value of the angle. This is because each division on the vernier scale is slightly smaller than the corresponding divisions on the main scale, allowing for the detection of minute differences.
This instrument is widely used in metalworking, carpentry, and quality inspection processes where precise angular measurement is required. The bevel protractor can measure both internal and external angles, making it versatile and practical. Its reliability and ease of use make it a preferred choice in workshops and laboratories.