# I - V Characteristics

1. Feb 15, 2005

### Matt.D

I've been given a Physics Assignment for my half term holiday, but I'm a little stuck with the following question. The topic is Electricity.

Question 2.

a) Draw the I - V characteristics for two components, A and B, both of which obey Ohm's Law. Component B has a lower resistance than component A. Lable your Characteristics as A and B.

b) Draw the I-V characteristics for a silicon semiconductor diode giving and relevant voltage values.

I don't know what it means by I - V characteristics. The components must obey Ohm's Law. Could someone elaborate on what I need to do.

Thanks

2. Feb 15, 2005

### xanthym

A device's "I-V Characteristics" indicate the relationship between the Voltage "V" across the device's terminals and the resulting Current "I" through the device. Each electronic device (resistor, diode, etc) has its own specific "I-V Characteristics".

For a Resistor, Ohm's Law provides the "I-V Characteristics". We have the familiar { V=I*R } equation, in which "R" is the resistance value, which can be solved for I:

$$:(1): \ \ \ \ I = \frac {V} {R}$$ :::::<---- "I-V Characteristics" for Resistor with Resistance "R"

Graphing "I-V Characteristics":
To graph "I-V Characteristics", designate the Vertical Axis to be "I" for the Current and designate the Horizontal Axis to be "V" for the Voltage. (It's standard technique to graph "I-V Characteristics" with "I" the dependent variable (i.e., Vertical Axis) and "V" the independent variable (i.e., Horizontal Axis) ). The relationship or formula would then be graphed the same way you'd graph an equation with variables "y" and "x".

From Equation #1 above, what would you expect the graph to look like, where you would graph it for a CONSTANT value of Resistance "R" (for instance, R=50 ohms)?
(Hint: A line in standard "x" and "y" equations is { y = m*x + b } )

For a Diode device, the "I-V Characteristics" are considerably more complex. You'll need to consult your textbook for the relationship between "I" and "V" for a Diode. In particular, a given Diode has a different relationship between "I" and "V" for different voltage ranges, and thus its graph will NOT just be a single straight line. The Diode, for instance, will behave differently with a Positive Voltage across it ("Forward Conduction Range") than with a Negative Voltage across it ("Reverse Blocking Range"). For the latter, there is also usually a "Breakdown Voltage" which will produce yet another different region on your graph. Again, consult your textbook for this information, or try the Web URL below.
http://www.antonine-education.co.uk/Electronics_AS/Electronics_Module_1/Topic_4/Topic_4__diodes.htm [Broken]

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Last edited by a moderator: May 1, 2017