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Ohmic and Non Ohmic Resistors

The current-v...

Question

The current-voltage graph for a device is shown in figure. The resistance is negative in region.

A

AB

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B

BC

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C

ABC

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D

None of these

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Solution

The correct option is A AB
According to the Ohm's law, the resistance is the voltage applied across resistor per unit current passing through it.
$R = \frac{V}{I}$
Hence $R = \frac{1}{I / V}$
$⟹ R = \frac{1}{s l o p e}$
Hence resistance is negative when the slope of the curve is negative.
Therefore resistance is negative in region AB.

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Q. Note that for nearly all materials the current - voltage relation is temperature dependent. Thus at low temperatures the curve in Fig.

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than at higher temperatures, and at successively higher temperatures the asymmetry in the curve becomes less and less pronounced.
The current - voltage relation for a source may also be represented graphically. For a source represented by

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V = E - I r

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V -

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