Ohm’s Law Resistance and Resistors
Resistance is the difficulty applied by the conductor to the current flowing through it. Each material has different resistance. We show resistance with R and unit of it is ohm (Ω).
1 Ω=resistance of the conductor when 1 A current flows under the 1 V potential difference. Resistance is represented with the following picture in circuits;
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Rheostat
Rheostat is a kind of device used to vary existing resistance. It is shown in the circuits as;
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Resistance of the conductor depends on;
· Types of the material or electrical resistivity of the material. It is shown with Greek letter ρ. Resistance of the material is linearly proportional to electrical resistivity.
· Length of the material (l). Resistance is linearly proportional to the length of the conductor.
· Cross-sectional are of the conductor. Resistance is inversely proportional to the cross-sectional area.
· Temperature. Temperature shows different effects with respect to the type of material.
We write resistance formula with the explanation given above as;
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Ohm’s Law
Ohm’s law gives the relation between voltage, current and resistance. According to Ohm, current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the conductor. We can summarize this explanation with the following formula;
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If we take resistance of the conductor constant, then potential difference and current of the system changes linearly as shown in the following graph;
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Example: Potential difference vs. Current graph of a conductor is given below, Find the behavior of resistance in intervals I, II and III.
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Ohm’s law states that V=I.R
- In the first interval, since the potential difference and current are linearly increases then the resistance of the system becomes constant.
- In the second interval, a potential difference is constant, however, current increases. This can be possible by decreasing the amount of resistance.
- In the third interval, current is constant, however, potential difference increases. This can be possible by increasing the amount of resistance.
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