Hi Kyle, Yes there are variable resistors. By using it you can adjust the resistance within a given range. (resistors provide us with a means of controlling the current and/or voltage present in a circuit). These are available in variety of forms,most popular of which are the carbon track and wirewound petentiometer (a 3 terminal variable resistor). Carbon potentiometer are available with liner and semi-logarithmic law tracks and in rotary or liner/slider formats. I would like to give few hints & tips of variable resistors.
Carbon track variable resistors suffer from noise and track wear. This makes them unacceptable for critical applications such as instrumentation, low-noise amplifiers etc. To give better control over output levels in audio applications, use log law potentiometers for volume controls. Carbon track controls should never be used for performing adjustments of output voltage in power suppliers as intermittent slider contract can sometimes result in the full output voltage being applied momentarily to the load ! (my experience)