What is the advantage of a metal film resistor over a carbon resistor?
The correct answer and explanation is :
Correct Answer:
A metal film resistor offers greater accuracy, stability, and lower noise compared to a carbon resistor.
300-Word Explanation:
Metal film resistors and carbon resistors are both commonly used in electronic circuits to limit current flow or divide voltages, but they differ significantly in their construction and performance characteristics.
Metal film resistors are made by depositing a thin layer of metal, typically nickel-chromium, onto a ceramic rod. The resistance value is precisely adjusted by cutting a spiral groove in the film with a laser. In contrast, carbon resistors (specifically carbon composition resistors) are made by mixing carbon powder with a binder to form a resistive element, which is then molded into a cylindrical shape.
One of the main advantages of metal film resistors is their high precision and tight tolerance. Tolerances can be as low as ±0.1%, whereas carbon resistors typically have tolerances around ±5% or even ±10%. This makes metal film resistors suitable for applications where exact resistance values are critical.
Another advantage is their thermal and electrical stability. Metal film resistors have a lower temperature coefficient, meaning their resistance changes less with temperature fluctuations. This results in more consistent performance over a wide temperature range, which is crucial in sensitive analog circuits and instrumentation.
Noise performance is also a key factor. Metal film resistors generate less electronic noise because of their homogeneous and stable material structure. Carbon resistors, on the other hand, can generate significant noise due to the granular nature of the carbon composition and irregular current paths.
Lastly, metal film resistors are more durable and have a longer lifespan under normal operating conditions, making them ideal for precision equipment.
In summary, while carbon resistors are cheaper and adequate for many general-purpose applications, metal film resistors are preferred in circuits requiring accuracy, low noise, and stability.