Ohmic vs. Non-Ohmic Materials

Definition

Ohmic materials are those that obey Ohm's Law, meaning their current-voltage (I-V) relationship is linear and consistent across different voltage levels. Non-ohmic materials, on the other hand, do not follow this law; their I-V characteristics can be nonlinear, meaning that the relationship between current and voltage can change depending on the applied voltage or current. This distinction is critical when analyzing electrical circuits and understanding how different materials respond under varying conditions.

5 Must Know Facts For Your Next Test

1. Ohmic materials include common conductors like copper and aluminum, where the resistance remains constant regardless of voltage changes.
2. Non-ohmic materials may include diodes and transistors, which exhibit nonlinear I-V characteristics crucial for various electronic applications.
3. The slope of an I-V graph for an ohmic material represents its resistance, while for non-ohmic materials, this slope can change based on the applied voltage.
4. Temperature can affect both ohmic and non-ohmic materials differently; for example, increasing temperature typically increases resistance in ohmic materials.
5. Understanding whether a material is ohmic or non-ohmic is essential for designing circuits, as it influences how components will behave under different electrical conditions.

Review Questions

• How do the I-V characteristics of ohmic materials differ from those of non-ohmic materials, and why is this difference important?
  • Ohmic materials display linear I-V characteristics, meaning their current increases proportionally with voltage, leading to a constant resistance. In contrast, non-ohmic materials exhibit nonlinear characteristics, where the relationship between current and voltage varies depending on conditions like temperature or applied voltage. This difference is important for understanding how different components function in a circuit, influencing design decisions and predicting circuit behavior.
• Evaluate how temperature impacts the resistance of ohmic versus non-ohmic materials and what implications this has for circuit design.
  • Temperature generally increases resistance in ohmic materials as they tend to have a positive temperature coefficient. For non-ohmic materials, the effect of temperature can lead to more complex changes in resistance due to their nonlinear properties. This means that circuit designs must account for these temperature effects to ensure reliable operation under varying thermal conditions, especially in sensitive applications like semiconductors.
• Analyze a practical application where distinguishing between ohmic and non-ohmic materials is crucial for engineering effective electrical circuits.
  • In power supply design, distinguishing between ohmic and non-ohmic materials is critical. For example, in a circuit involving both resistors (ohmic) and diodes (non-ohmic), understanding their behavior under different voltages ensures that the circuit functions correctly. If an engineer mistakenly assumes that a diode behaves like a resistor, they could miscalculate current flow, potentially damaging components or leading to circuit failure. Thus, knowing how each material behaves allows engineers to optimize performance and reliability.

Related terms

Ohm's Law:

A fundamental principle in electronics stating that the current through a conductor between two points is directly proportional to the voltage across the two points.

Resistance:

A measure of the opposition to current flow in an electrical circuit, often represented by the symbol 'R' and measured in ohms.

Semiconductors:

Materials that have electrical conductivity between that of conductors and insulators, often exhibiting non-ohmic behavior.