Distinguish between ohmic and non ohmic substances; explain with … - Vidyadip

Question

Distinguish between ohmic and non ohmic substances; explain with the help of example.

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Answer

Ohmic substances	Non-ohmic substances
1. Substances which obey ohm’s law are called ohmic substances.	Substances which do not obey ohm’s law are called non-ohmic substances.
2. Potential difference (V) versus current (I) curve is a straight line.	Potential difference (V) versus current (I) curve is not a straight line.
3. Resistance of these substances is constant i.e. they follow linear I-V characteristic.	Resistance of these substances
<p>Expression for resistance is, $R =\frac{V}{I}$</p>	<p>Expression for resistance is,<br />$<br />R =\lim _{\Delta I \rightarrow 0} \frac{\Delta V}{\Delta I}=\frac{d V}{d I}<br />$</p>
Examples: Gold, silver, copper etc.	Examples: Liquid electrolytes, vacuum tubes, junction diodes, thermistors etc.

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