# If the coefficient of adhesion on dry rails 0.25. which of the following could be the value for wet rails?

### Right Answer is:

0.15

#### SOLUTION

**Adhesive weight:-** The total weight to be carried out on the drive-in wheels of a locomotive is known as adhesive weight.

**Coefficient of adhesion:-** It is deemed as the ratio of the tractive effort required to propel the wheel of a locomotive to its adhesive weight

**µ = F _{t}/W**

Where

F_{t} = Tractive effort

W = Adhesive Weight

The coefficient of adhesion may be viewed as the coefficient of friction between the tyre of a wheel at rest and the rail. If the diameters of all the wheels were exactly the same, then the conditions of adhesion would also be the same regardless of whether the locomotive was at rest or moving. But in practice, there are always some very small differences between the wheel diameters and therefore, the wheels cannot turn on the track all at the same speed and without a certain amount of slipping. Since even the smallest amount of slipping reduces the coefficient of friction, the value of adhesion must also decrease. The magnitude of adhesion depends on the material used for making the wheel tyres and rails as well as on the state of both the wheel tires and the rails.

In traction calculations, the coefficient e is usually obtained from tables assembled from experimental data

No | State of Rail | µ Value of Steel |
µ Value of Cast Iron |

1 | Rail Dry with sanding | 0.30 − 0.33 | 0.25 |

2 | Rail Dry without sanding | 0.25 | 0.25 |

3 | Rail Moist | 0.20 | 0.15 |

4 | Rail Wet | 0.05 − 0.15 | 0.05 − 0.10 |

So according to the above table if the value of Dry rail is 0.25 then the value of Wet Rail is dry rails 0.05 − 0.15