Variable and fixed resistors?

Question

What's the advantage over using a variable resistor rather than a fixed one? Other than the obvious fact that you can change the resistance, especially in an experiment where you are investigating the effect of legnth of wire on resistance, where you measure current and voltage to work our resistance.

Answer 1

In this case, I have 3 points pinpointing that fixed resistor is better than variable resistor.

Fixed resistor are far more inexpensive than variable resistor since variable resistors have more moving parts than fixed resistors.

Every variable resistor has a negative resistance. That is on a point that when we tilt the variable resistor to increase the resistance, on the up-going slope, there will be a sudden down and up hill. This always become the error for variable resistors as the tilted section is not actually providing the required resistance.

Variable resistors come from a variety of types. There are carbon powder variable resistor (VB), sliding coil VB, chip VB or solid-state VB. In carbon powder and sliding coil VBs, the least resistance section will heat up very fast as it is like a short circuit, and destroy the VB at ease.

Answer 2

If I make a voltage divider with a variable resistor, I can control the voltage between two particular points in the circuit. Variable resistors, also called potentiometers, are also used to control volume (when you turn the volume on something up or down you are changing the resistance of a variable resistor).

Answer 3

There are many advantages. For example, in a manufacturing process, where some kind of calibration must take place, you can install a variable resistor on the circuit board, and then once the device is fully assembled, it could be adjusted to set some operating parameter.

Another obvious example would be a volume control (although most are digitally controlled, now!). A fixed resistor is of no value here.

Answer 4

You should never use a variable resistor where a fixed one will do, 'cos they cost a lot more! That said, VRs are necessary in analogue circuits that have to be accurately adjusted, to compensate for the fact that other components in the circuit change their characteristics with age and temperature.

As you say, VRs are also useful in experimentation. Sometimes, when designing a circuit, it's very difficult to calculate the exact value of resistor required at some point. So stick in a VR, wind it around until the circuit works, then measure its resistance and replace it by the nearest fixed value. Cheating -- but it works!

Answer 5

One example is the variable resistor in your gas tank controlled by a float attached to a pivoting arm. This enables The indicator on the dash-board to tell you how much gas is left in your tank. You also have variable resistor dimmer switches to control lighting. And the variable resistor volume knob on your radio.

Answer 6

A dimmer switch.