Wiring a Pot

[Old Grey]

This is going to sound pretty basic, but when wiring a variable resistor to ground why do people tie the free end back to the wiper.

For example I have a car sensor, like the coolant temp sensor, that is just a temp dependant variable resistor to ground.
Now I want to simulate it on the bench with a pot, so I connect one of the pot's outer contacts to GND, and my circuit to the middle wiper. This leaves one free contact on the pot, which I see in some circuits being tied back to the wiper.

If you look at the 3 pots - middle left -, 2 are tied, 1 not.

 

[Chemelec]

If the Wiper Looses Contact with no connection to the one terminal, than the resistance goes to Infinity.
If the Center in connected to the Center, than it just goes to the Total Resistance of the pot.

This is better as it offers PROTECTION from damage to other parts in some situations.

 

[Old Grey]

Ahh, so I will tie them all to the wiper from now on.

Thanks

 

[Alec_t]

Ahh, so I will tie them all to the wiper from now on.

That would be appropriate only if the pot is being used as a rheostat (as distinct from a potential divider).

 

[Chemelec]

The Initial Question is about a FREE END, Unused Terminal on a Pot.
Not about Volume controls or Voltage Dividers where all 3 terminals are being used.