For Which Of The Following Substances, Resistance Decreases With Increase In Temperature?1). Copper 2). Mercury 3). Carbon 4). Platinum ​

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Temperature and Electrical Resistance: Understanding the Relationship

Introduction

When it comes to electrical resistance, most people assume that it remains constant, regardless of the temperature. However, this is not always the case. In fact, the relationship between temperature and electrical resistance is complex, and it varies depending on the substance in question. In this article, we will explore which substances exhibit a decrease in resistance with an increase in temperature.

Understanding Electrical Resistance

Before we dive into the specifics of temperature and electrical resistance, let's take a moment to understand what electrical resistance is. Electrical resistance is a measure of the opposition to the flow of electric current through a conductor. It is measured in ohms (Ω) and is typically denoted by the symbol R. The resistance of a conductor depends on several factors, including its length, cross-sectional area, and the material it is made of.

Temperature and Electrical Resistance: The General Rule

In general, the resistance of a conductor increases with an increase in temperature. This is because the atoms or molecules of the conductor vibrate more rapidly as the temperature rises, which creates more collisions between the charge carriers (such as electrons) and the atoms or molecules of the conductor. These collisions reduce the flow of electric current, resulting in an increase in resistance.

Exceptions to the Rule: Substances with Decreasing Resistance

While the general rule is that resistance increases with temperature, there are some substances that exhibit a decrease in resistance with an increase in temperature. These substances are typically metals, and they are known as "negative temperature coefficient" (NTC) materials.

1. Copper

Copper is one of the most widely used metals in electrical applications, and it is known for its high electrical conductivity. However, copper is not an NTC material, and its resistance increases with temperature. In fact, copper's resistance increases by about 0.4% for every degree Celsius rise in temperature.

2. Mercury

Mercury is a liquid metal that is often used in thermometers and other temperature-sensing devices. It is also an NTC material, meaning that its resistance decreases with an increase in temperature. Mercury's resistance decreases by about 0.1% for every degree Celsius rise in temperature.

3. Carbon

Carbon is a versatile element that can exist in many different forms, including graphite and diamond. While carbon is not typically thought of as a metal, it can exhibit metallic properties under certain conditions. In fact, carbon nanotubes have been shown to exhibit NTC behavior, meaning that their resistance decreases with an increase in temperature.

4. Platinum

Platinum is a rare and valuable metal that is often used in high-temperature applications. While platinum is not typically thought of as an NTC material, it does exhibit a negative temperature coefficient of resistance at very high temperatures. However, this effect is relatively small, and platinum's resistance increases by about 0.1% for every degree Celsius rise in temperature.

Conclusion

In conclusion, while most substances exhibit an increase in resistance with an increase in temperature, there are some exceptions to the rule. Substances like mercury, carbon, and platinum exhibit a decrease in resistance with an increase in temperature, making them useful for applications where high-temperature stability is required. By understanding the relationship between temperature and electrical resistance, we can design more efficient and effective electrical systems that take advantage of these unique properties.

References

  • [1] "Electrical Resistance and Temperature" by the National Institute of Standards and Technology (NIST)
  • [2] "Negative Temperature Coefficient Materials" by the American Society for Metals (ASM)
  • [3] "Carbon Nanotubes: Properties and Applications" by the Royal Society of Chemistry (RSC)

Further Reading

  • "Temperature and Electrical Resistance: A Review" by the Journal of Electrical Engineering
  • "Negative Temperature Coefficient Materials: A Review" by the Journal of Materials Science
  • "Carbon Nanotubes: A Review of Their Properties and Applications" by the Journal of Nanoscience and Nanotechnology
    Temperature and Electrical Resistance: A Q&A Guide

Introduction

In our previous article, we explored the relationship between temperature and electrical resistance, and we discussed the substances that exhibit a decrease in resistance with an increase in temperature. In this article, we will answer some of the most frequently asked questions about temperature and electrical resistance.

Q: What is the general rule for temperature and electrical resistance?

A: The general rule is that the resistance of a conductor increases with an increase in temperature. This is because the atoms or molecules of the conductor vibrate more rapidly as the temperature rises, which creates more collisions between the charge carriers (such as electrons) and the atoms or molecules of the conductor.

Q: What are NTC materials, and how do they behave?

A: NTC materials are substances that exhibit a decrease in resistance with an increase in temperature. These materials are typically metals, and they are used in applications where high-temperature stability is required.

Q: Which substances exhibit a decrease in resistance with an increase in temperature?

A: Some substances that exhibit a decrease in resistance with an increase in temperature include mercury, carbon, and platinum. However, it's worth noting that these substances are not typical NTC materials, and their behavior may vary depending on the specific application.

Q: Why do some substances exhibit a decrease in resistance with an increase in temperature?

A: There are several reasons why some substances may exhibit a decrease in resistance with an increase in temperature. One reason is that the increased thermal energy can cause the atoms or molecules of the substance to vibrate more rapidly, which can lead to a decrease in resistance. Another reason is that the increased temperature can cause the substance to undergo a phase transition, such as a change from a solid to a liquid, which can also lead to a decrease in resistance.

Q: What are some common applications of NTC materials?

A: NTC materials are used in a variety of applications, including temperature-sensing devices, thermometers, and high-temperature electrical systems. They are also used in applications where high-temperature stability is required, such as in the aerospace and automotive industries.

Q: How do I choose the right NTC material for my application?

A: When choosing an NTC material, you should consider several factors, including the temperature range, the required resistance value, and the desired level of stability. You should also consider the specific properties of the material, such as its thermal conductivity, electrical conductivity, and mechanical strength.

Q: What are some common mistakes to avoid when working with NTC materials?

A: Some common mistakes to avoid when working with NTC materials include:

  • Not considering the temperature range of the material
  • Not selecting a material with the correct resistance value
  • Not taking into account the material's thermal conductivity and electrical conductivity
  • Not considering the material's mechanical strength and durability

Q: What are some future developments in the field of NTC materials?

A: There are several future developments in the field of NTC materials, including the development of new materials with improved properties, such as higher thermal conductivity and electrical conductivity. There is also a growing interest in the use of NTC materials in emerging technologies, such as nanotechnology and biotechnology.

Conclusion

In conclusion, temperature and electrical resistance are complex topics that require a deep understanding of the underlying physics. By understanding the relationship between temperature and electrical resistance, we can design more efficient and effective electrical systems that take advantage of the unique properties of NTC materials. We hope that this Q&A guide has provided you with a better understanding of the topic and has helped you to avoid some common mistakes.

References

  • [1] "Electrical Resistance and Temperature" by the National Institute of Standards and Technology (NIST)
  • [2] "Negative Temperature Coefficient Materials" by the American Society for Metals (ASM)
  • [3] "Carbon Nanotubes: Properties and Applications" by the Royal Society of Chemistry (RSC)

Further Reading

  • "Temperature and Electrical Resistance: A Review" by the Journal of Electrical Engineering
  • "Negative Temperature Coefficient Materials: A Review" by the Journal of Materials Science
  • "Carbon Nanotubes: A Review of Their Properties and Applications" by the Journal of Nanoscience and Nanotechnology