Which of the following is an example of non-ohmic resistance?

Explanation:

Understanding Non-Ohmic Resistance

Definition: Non-ohmic resistance refers to materials or components in which the current flowing through them does not vary linearly with the applied voltage. This non-linear relationship means that these materials do not obey Ohm's Law, which states that V = I × R, where V is the voltage, I is the current, and R is the resistance. Non-ohmic materials exhibit a variable resistance depending on the voltage and current conditions.

Correct Option Analysis:

The correct option is:

Option 2: Diode

A diode is a semiconductor device that allows current to flow in one direction only. The relationship between the voltage across the diode and the current through it is highly non-linear, which makes the diode a classic example of a non-ohmic resistor. In a diode, the current does not increase proportionally with an increase in voltage. Instead, the diode has a threshold voltage (forward voltage) that must be exceeded for significant current to flow. Below this threshold, the current is negligible. Once the threshold is crossed, the current increases rapidly with a small increase in voltage, leading to a non-linear I-V (current-voltage) characteristic.

Important Information:

To further understand the analysis, let’s evaluate the other options:

Option 1: Tungsten

Tungsten is a metal commonly used in incandescent light bulb filaments. It exhibits ohmic behavior at lower temperatures, meaning it follows Ohm’s Law where the resistance remains constant regardless of the applied voltage. However, at higher temperatures, its resistance increases, but this change is gradual and not highly non-linear, making it less representative of non-ohmic behavior compared to a diode.

Option 3: Copper

Copper is a highly conductive metal used in electrical wiring. It is an ohmic conductor, meaning its resistance remains constant and it follows Ohm’s Law. The current through copper varies linearly with the applied voltage, making it an example of ohmic resistance.

Option 4: Carbon

Carbon can exhibit both ohmic and non-ohmic behavior depending on its form and usage. In the form of graphite, it behaves as an ohmic conductor. However, in other forms, such as in certain composite materials or at very high temperatures, carbon can show non-linear resistance characteristics. Nevertheless, its behavior is not as distinctly non-ohmic as that of a diode.

Conclusion:

Understanding non-ohmic resistance is essential for distinguishing materials and components based on their electrical properties. A diode exemplifies non-ohmic resistance due to its highly non-linear current-voltage relationship, making it the correct choice among the given options. Tungsten, copper, and carbon, while they may exhibit variations in resistance under certain conditions, do not display the distinct non-linear characteristics seen in diodes, and hence are not examples of non-ohmic resistance in the same context.