Circuit Components-Variable resistors

[wei1006]

Homework Statement

As contact point Y moves to X, the lamps becomes brighter. Why is this so?

Homework Equations

R=p (length/Area)
I=V/R

The Attempt at a Solution

As Y moves closer to X, length of wire decreases, hence resistance decreases and brightness of lamp increases.

I am not clear of the concept of brightness of lamp and resistance of wire. Please help, thank you![/B]

 

[andrevdh]

The lamp is in a series circuit with a power supply with a fixed voltage. What would make the light bulb burn brighter?