Electricity

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Electrical components

Characteristic curve of a resistor

1) What is a characteristic curve ?

Definition: A characteristic curve is the graph on which are represented the variations in the voltage at the terminals of a component as a function of the current passing through it.

2) How to draw the characteristic curve of a resistor ?

To draw the characteristic curve of resistor we need the following circuit:


This circuit consists of a battery providing a variable voltage, a resistor, an ammeter and a voltmeter.
If the voltage of the battery changes there is a variation of voltage for the resistor and also a variation of electric current.
The measuring instruments are used to determine several couples of values ​​(voltage and current).
These couples are the coordinates of points used to draw the characteristic curve on a graph with the current on abscissa axis(horizontal axis) and the voltage on ordinate axis (vertical axis).

3) Properties of the characteristic curve of a resistor


The characteristic curve of a resistor is always a line passing through the origin point.
This line indicates that the voltage of the resistor is proportional to the current.
The proportionality coefficient corresponds to the resistance.
example:
For a 10 ohm resistor we obtain, thanks to the measures, the following points:
(I = 0.1 A, U = 1 V), (I = 0.2 A, U = 2 V), (I = 0.3 A, U = 3 V)
(I = 0.4 A, U = 4 V) etc.
These values ​​are used to draw the following graph:


The voltage is ten time greater than current: ten is also the resistance.

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