1 Answer
Ohm's law, which states that \( V = I \cdot R \) (Voltage = Current × Resistance), is valid for most materials under normal conditions. However, there are two main situations where Ohm's law fails:
1. Non-Linear Materials (Non-Ohmic Conductors):
- What happens? Some materials do not have a constant resistance. Instead, their resistance changes with voltage or current. This means the relationship between voltage and current is not linear. For example, diodes, transistors, and certain semiconductors exhibit this behavior.
- Why does it happen? In these materials, the resistance is not constant because their internal structure or properties change with varying electrical conditions. As a result, the current-voltage relationship doesn't follow Ohm’s law.
2. High Voltage or High Current (Extreme Conditions):
- What happens? At very high voltages or currents, materials like metals may experience a phenomenon called electrical breakdown or thermal effects (like overheating), which leads to changes in resistance.
- Why does it happen? When the voltage or current gets too high, the material may begin to behave differently. For example, the heat generated from high current can cause the resistance of conductors to increase, or the material may even start to break down (like in a spark or arc). In such extreme cases, Ohm’s law doesn't hold because the relationship between voltage, current, and resistance changes under these conditions.
In summary, Ohm's law fails when materials are non-linear (like diodes) or when extreme electrical conditions cause the material’s resistance to change.
1. Non-Linear Materials (Non-Ohmic Conductors):
- What happens? Some materials do not have a constant resistance. Instead, their resistance changes with voltage or current. This means the relationship between voltage and current is not linear. For example, diodes, transistors, and certain semiconductors exhibit this behavior.- Why does it happen? In these materials, the resistance is not constant because their internal structure or properties change with varying electrical conditions. As a result, the current-voltage relationship doesn't follow Ohm’s law.
2. High Voltage or High Current (Extreme Conditions):
- What happens? At very high voltages or currents, materials like metals may experience a phenomenon called electrical breakdown or thermal effects (like overheating), which leads to changes in resistance.- Why does it happen? When the voltage or current gets too high, the material may begin to behave differently. For example, the heat generated from high current can cause the resistance of conductors to increase, or the material may even start to break down (like in a spark or arc). In such extreme cases, Ohm’s law doesn't hold because the relationship between voltage, current, and resistance changes under these conditions.
In summary, Ohm's law fails when materials are non-linear (like diodes) or when extreme electrical conditions cause the material’s resistance to change.