# MCQs on Worm Gears

1 - Question

Worm gear drives are used to transmit power between two non-intersecting shafts which are generally at right angles to each other.

a) True
b) False

Explanation: This is how the worm gear design fits into use.

2 - Question

The worm and worm wheel both are threaded screw.

a) True
b) Worm wheel is a toothed gear
c) Worm is a toothed gear
d) None of the listed

Explanation: Worm wheel is a toothed gear.

3 - Question

Which of the following is not true about worm gears?

a) Compact
b) Smooth and silent operation
c) Low speed reduction
d) All the mentioned are true

Explanation: Speed reduction can be high up to 100:1.

4 - Question

Is it possible to use worm gears in cranes for lifting purpose?

a) True
b) No self-locking and hence not possible
c) Possible up to a threshold load
d) None of the listed

Explanation: Worm gears support self-locking operation and hence are advantageous to use in lifting operations.

5 - Question

The power transmitting capacity of worm gears is high although efficiency is low.

a) True
b) False

Explanation: Both power transmitting capacity and efficiency of worm gears are low.

6 - Question

Can worm gears be used in steering mechanism?

a) True
b) False

Explanation: In steering mechanism, efficiency is of little importance but major requirement is of large mechanical advantage.

7 - Question

The worm helix angle is the _____ of the worm lead angle.

a) Complement
b) Half
c) Double
d) Supplement

Explanation: Worm helix angle+worm lead angle=90⁰.

8 - Question

If worm helix angle is 30⁰, then worm should have at least ___ threads.

a) 5
b) 6
c) 7
d) 8

Explanation: The permissible helix angle is 6⁰ and hence there should be at least five threads i.e. 30/6.

9 - Question

A pair of worm gear is written as 2/40/12/6. Calculate the centre distance.

a) 40mm
b) 156mm
c) 200mm
d) 80mm

Explanation: C=m(q+z)/2 where m=6mm, q=12 and z=40.

10 - Question

A pair of worm gear is written as 2/40/12/6. Calculate the speed reduction.

a) 2
b) 20
c) 15
d) 6

Explanation: i=40/2.

11 - Question

A pair of worm gear is written as 2/40/12/6. Calculate the pitch circle diameter of worm wheel.

a) 72mm
b) 240mm
c) 260mm
d) 320mm

Explanation: d=mxz where m=6mm and z=40.

12 - Question

A pair of worm gear is written as 2/40/12/6. Calculate the throat diameter of the worm wheel.

a) 220.5mm
b) 246.4mm
c) 190.44mm
d) 251.7mm

Explanation: d(t)=m[z+4cosϒ-2] where ϒ=9.46⁰ is the lead angle. tanϒ=2/12, z=40 and m=6mm.

13 - Question

A pair of worm gear is written as 2/40/12/6. Calculate the root diameter of the worm wheel.

a) 186.22mm
b) 250.4mm
c) 225.6mm
d) 250.44mm

Explanation: d=m[z-2-0.4cosϒ] where ϒ=9.46⁰ is the lead angle. tanϒ=2/12, z=40 and m=6mm.

14 - Question

If tangential force on worm is 1500N, then axial force on worm wheel will be?

a) 1500N
b) 3000N
c) 1500√2 N
d) 750N