# Variable Resistor

Linear variable resistor in electrical systems

## Library

Electrical Elements

## Description

The Variable Resistor block models a linear variable resistor, described with the following equation:

`$V=I·R$`

where

 `V` Voltage `I` Current `R` Resistance, i.e., the value presented at the control port

Connections + and – are conserving electrical ports corresponding to the positive and negative terminals of the resistor, respectively. P is a physical signal input port that controls the resistance value. The current is positive if it flows from positive to negative, and the voltage across the resistor is equal to the difference between the voltage at the positive and the negative terminal, V(+) – V(–).

## Dialog Box and Parameters

### Parameters Tab

Minimum resistance R>=0

The minimum resistance value. If the input signal falls below this level (for example, turns negative), this minimum resistance value is used. The parameter value must be nonnegative. The default value is `0`.

### Variables Tab

Use the Variables tab in the block dialog box (or the Variables section in the block Property Inspector) to set the priority and initial target values for the block variables prior to simulation. For more information, see Set Priority and Initial Target for Block Variables.

## Ports

The block has the following ports:

`+`

Electrical conserving port associated with the resistor positive terminal.

`-`

Electrical conserving port associated with the resistor negative terminal.

`P`

Physical signal input port that provides the resistance value.