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Ohm's law |
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Potential difference flowing through a conductor is directly proportional to the electric current when the temperature and other physical properties are kept constant.
\(V = I\times R\)
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If Ohm's law is obeyed, the graph against it or otherwise is a straight line as follows:
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Ohmic conductor |
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Conductor which obeys Ohm's Law (Resistance constant)
Example: Constantan wire
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Non-ohmic conductor |
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Conductor which does not obeys Ohm's Law (Resistance constant)
Example: Filament bulb
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Resistance of wire |
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\(R=\dfrac{\rho\,l}{A}\) |
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Factors that affect the resistance of a wire
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- Length of wire, \(l\)
- \(l\) increase, \(R\) increase
- cross sectional area of wire, \(A\)
- \(A\) increase, \(R\) decrease
- resistivity of the wire, \(\rho\)
- \(\rho\) increase, \(R\) increase
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Resistivity of a conductor, \(\rho\) |
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- a measure of a conductor's ability to oppose the flow of electric current
- unit is ohm-meter
- depends on the temperature and the nature of the conductor material
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