# Engineering Metrology Questions and Answers – Involute Curve

This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Involute Curve”.

1. What is the alternative name of involute gears?
a) Straight tooth gear
b) Helical gear
c) Cycloid gear
d) Spiral gear

Explanation: Commonly used forms of gear teeth are:
(i) involute
(ii) cycloidal
Involute gears are also called spur gears and straight tooth.

2. Where does involute gear is used?
a) For crude purposes
b) General purpose in precision engineering
c) Where heavy loads comes on machine
d) Where impact loads comes on machine

Explanation: Involute gears are used for general purpose in precision engineering. The cycloidal gears are not used in modern engineering generally, but can be used for some crude purposes where impact and heavy loads come on the machine.

3. What type of teeths is present in involute rack?
a) Spiral
b) Helical
c) Straight
d) Double helical

Explanation: The straight teeth are present in involute rack. Only a simple cutter is needed to form the complex involute form on gear. It is an advantage which is associated with involute curve or profile.

4. Upon which factor, shape of involute curve depends?
a) Base circle diameter
b) Pitch circle diameter
d) Face width

Explanation: The shape of involute curve entirely depends upon the diameter of base circle as involute is generated from a base circle. Pressure angle and pitch also important for the profile of involute.

5. Which of the following is correct about involute curve?
a) Involute curvature increases with increase in base circle diameter
b) Involute is straight line when diameter of base circle is zero
c) Involute curvature increases with increase in pitch circle diameter
d) Involute curvature decreases with increase in base circle diameter

Explanation: The curvature of the involute decreases as the diameter of base circle goes on increasing and when diameter of base circle is infinity then finally involute becomes straight line.
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6. What is the standard pressure angle for an involute system?
a) 20 or 14.5 degree
b) 20 or 30 degree
c) 30 or 14.5 degree
d) 40 or 30 degree

Explanation: The involute system has a standard value of pressure angle which is 20° or 14.5° whereas on the cycloidal system does not have a standard pressure angle, it varies from zero at pitch line to a maximum at the teeth tips.

7. Which of the following is true for an involute curve?
a) Tangent to any point on involute is parallel to the generator at that point
b) Tangent to any point on involute is perpendicular to the generator at that point
c) Tangent to any point on involute is at 45 degree to the generator at that point
d) Tangent to any point on involute is at 30 degree to the generator at that point

Explanation: It is important to fulfill the requirements of law of gearing for an involute curve. The tangent at any point on involute will be perpendicular to the generator at that point. This condition fulfils the requirements needed for laws of gearing.

8. What is the effect of centre distance between two gears on velocity ratio of involute gear pair?
a) Less for less velocity ratio
b) Less for more in velocity ratio
c) More or less for more velocity ratio
d) No effect

Explanation: Variations in the centre distance between 2 gears have no effect on the velocity ratio between an involute gears pair. It is an advantage associated with the involute for the flank curve of gear.

9. What is the involute curve?
a) Point Locus on a straight line which rolls around a circle without slipping
b) Point Locus on a straight line which rolls around a line without slipping
c) Point Locus on a circle which rolls around a pitch circle without slipping
d) Point Locus on a circle which rolls around a line without slipping

Explanation: An involute curve is a point locus on straight line which rolls, around a circle without slipping. It could also be defined as the point locus on a piece of string which in unwound from a cylinder or stationary cylinder.

10. Which of the following factor is least important for an involute profile?
a) Number of teeth
b) Pressure angle
c) Pitch
d) Gear it mates with

Explanation: The involute gear profile is important in machine design, since unlike with other gear systems, involute gear tooth profile depends on only the number of teeth on the gear, pitch and pressure angle but does not depend on the gear it mates with.

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