Gujarat BoardEnglish MediumSTD 10Scienceelectricity3 Marks
Question
Which law gives relation between potential difference across a metallic wire and current through it ? Describe it in brief.
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Answer
Ohm's law gives relation between potential difference across a metallic wire and current through it. This law was deduced experimentally by German physicist, George Simon Ohm. It can be stated as follows. °Statement : → "Potential difference $(V)$ across a current carrying metallic wire is directly proportional to current $(I)$ flowing through it, provided temperature of wire remains constant." → Mathematically, $V \propto I$ $ \therefore \quad \frac{V}{I}=\text { constant } $ → Here ratio $\frac{V}{I}$ remains constant for a given metallic wire at a given temperature. Such a constant ratio is called "resistance" of a given metallic wire, shown by symbol $R$. It is the property of a conductor to resist the flow of charges through it. Thus, $ \frac{V}{I}=R $ → Electrical component having resistance is called "resistor" → SI unit of resistance is ohm, shown by symbol $\Omega$. → Equation (2) gives mathematical form of Ohm's law. Writing $S I$ units in equation (2), $ \frac{\text { volt }}{\text { ampere }}= Ohm $ → Using symbols, $\Omega=\frac{V}{A}=V A^{-1}$
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