Resistance & Resistivity - How Temperature Affects Resistance

Joe Robinson Training
2 Oct 201809:31
EducationalLearning
32 Likes 10 Comments

TLDRThis educational video explores the impact of temperature, length, and cross-sectional area on electrical resistance. It demonstrates through experiments that lowering temperature reduces resistance, while increasing length and cross-sectional area have opposite effects. The results emphasize the direct proportionality between resistance and temperature and the inverse relationship between resistance and cross-sectional area, highlighting the importance of these factors in electrical applications.

Takeaways
  • 📈 The resistance of a conductor is directly proportional to its length; doubling the length doubles the resistance.
  • 📊 The resistance of a conductor is inversely proportional to its cross-sectional area; doubling the area halves the resistance.
  • 🌡️ The resistance of most materials, including copper, increases with temperature; higher temperature leads to higher resistance.
  • ❄️ Lowering the temperature of a conductor, such as by placing it in a freezer, reduces its resistance.
  • 🔥 Raising the temperature of a conductor, such as by heating it, increases its resistance.
  • 🔧 Measuring the resistance of a 100-meter cable with 1mm² cross-sectional area yielded 1.78 ohms at room temperature.
  • 🛠️ Doubling the length and cross-sectional area of the conductor while keeping the temperature constant results in a quadruple increase in resistance.
  • 🔄 Experiments showed that resistance can be manipulated by altering the conductor's length, cross-sectional area, and temperature.
  • 🎥 A time-lapse experiment demonstrated the effect of temperature increase on resistance, showing a rise in resistance as the cable heated up.
  • 📚 Understanding the relationship between resistance, length, cross-sectional area, and temperature is crucial for electrical engineering and cable design.
  • 🚫 The experiment involving heating the cable should not be attempted at home due to the risk of fire and should be conducted under controlled conditions.
Q & A

  • What is the main topic of the training video?

    -The main topic of the training video is the exploration of resistance and resistivity in electrical conductors, specifically focusing on how factors like length, cross-sectional area, and temperature affect resistance.

  • What was the initial resistance measurement of the 100-meter drum of cable?

    -The initial resistance measurement of the 100-meter drum of cable was 1.78 ohms.

  • How did doubling the length and cross-sectional area of the conductor affect its resistance?

    -Doubling the length of the conductor doubled its resistance, while doubling the cross-sectional area halved the resistance, maintaining a direct proportionality between length and resistance, and an inverse proportionality between cross-sectional area and resistance.

  • What is the ambient temperature in the experiment, and how does it affect the resistance of a conductor?

    -The ambient temperature refers to the temperature of the air surrounding the conductor. In the experiment, it was observed that reducing the ambient temperature by cooling the cable in a freezer decreased its resistance.

  • What was the final resistance measurement of the cable after it was heated?

    -After heating the cable, the final resistance measurement increased to 2.04 ohms, demonstrating that increasing the temperature of the conductor also increases its resistance.

  • What happens to the resistance when the conductor's temperature is reduced below ambient temperature?

    -When the conductor's temperature is reduced below ambient temperature, such as by placing the cable in a freezer, the resistance decreases.

  • What is the relationship between the length of a conductor and its resistance?

    -The resistance of a conductor is directly proportional to its length. If the length of the conductor is doubled, the resistance also doubles.

  • What is the relationship between the cross-sectional area of a conductor and its resistance?

    -The resistance of a conductor is inversely proportional to its cross-sectional area. If the cross-sectional area is doubled, the resistance is effectively halved.

  • Why should the experiment with heating the cable not be attempted at home?

    -The experiment with heating the cable should not be attempted at home due to the risk of fire. It should only be conducted under controlled conditions for safety reasons.

  • How did the time-lapse video demonstrate the effect of temperature on resistance?

    -The time-lapse video showed that as the cable got hotter, its resistance increased. This illustrates that for most materials, including the copper in the cable, increasing temperature leads to increased resistance.

  • What is the summary of the key principles learned from the videos?

    -The key principles learned from the videos are that increasing the length of a conductor increases its resistance (direct proportionality), increasing the cross-sectional area decreases its resistance (inverse proportionality), and increasing the temperature of the conductor also increases its resistance (direct proportionality).

Outlines
00:00
🔬 Experimenting with Temperature's Impact on Cable Resistance

This paragraph details an experiment that investigates the effect of temperature on the resistance of a conductor. Initially, a 100-meter drum of cable with a 1mm² cross-sectional area is measured to have a resistance of 1.78 ohms at room temperature. The cable is then placed in a freezer overnight, resulting in a significant temperature drop and a consequent decrease in resistance to 1.66 ohms. The experiment further explores the relationship between resistance and temperature by demonstrating that reducing the temperature of the conductor leads to a reduction in resistance, a phenomenon consistent with most conductive materials.

05:00
🌡️ The Influence of Temperature and Length on Conductor Resistance

The second paragraph continues the exploration of conductor resistance by examining how increasing the temperature affects it. A cold drum of cable is placed above heaters, and a time-lapse experiment shows the resistance increasing as the cable warms up. An accurate measurement after heating reveals the resistance has risen to 2.04 ohms, a considerable increase from the original 1.78 ohms at room temperature. The paragraph reinforces the principle that for most materials, including copper, increasing temperature results in increased resistance. The video concludes by summarizing the key takeaways: increasing length and temperature both lead to increased resistance, while increasing cross-sectional area decreases resistance.

Mindmap
Keywords
💡Resistance
Resistance is a fundamental concept in physics and electrical engineering, referring to the opposition a material offers to the flow of electric current. In the context of the video, resistance is the key parameter being measured and analyzed in experiments with the cable. The resistance of the conductor is found to be affected by factors such as length, cross-sectional area, and temperature. For instance, the video shows that a 100-meter drum of 1 mm² cable has a resistance of 1.78 ohms at room temperature.
💡Resistivity
Resistivity is a property of materials that quantifies how strongly the material opposes the flow of electric current. It is an intrinsic property and is dependent on the material's type, temperature, and sometimes its structure. In the video, resistivity is the underlying property that influences the resistance of the conductor. The discussion on how resistance changes with temperature is directly related to the resistivity of the cable material.
💡Ambient Temperature
Ambient temperature refers to the temperature of the surrounding environment in which an object is placed. In the video, the ambient temperature is a critical factor affecting the resistance of the conductor. The experiment demonstrates that lowering the ambient temperature by placing the cable in a freezer reduces the resistance of the cable, while increasing the temperature by heating it causes the resistance to rise.
💡Conductor
A conductor is a material that allows the flow of electric current due to the presence of free charge carriers, such as electrons. In the video, the cable is the conductor under examination. The resistance of the conductor is measured and manipulated by changing its length, cross-sectional area, and the ambient temperature to observe how these variables affect the electrical resistance.
💡Cross-Sectional Area
Cross-sectional area refers to the internal area of a two-dimensional slice of a three-dimensional object. In the context of the video, the cross-sectional area of the cable is an important factor that influences its resistance. The experiment shows that doubling the cross-sectional area of the cable effectively halves its resistance, illustrating an inverse relationship between the cross-sectional area and resistance.
💡Length
Length is a measure of the extent of an object in space along a specific direction. In the context of the video, the length of the cable is a key factor in determining its resistance. It is demonstrated that doubling the length of the conductor also doubles its resistance, highlighting a direct proportionality between length and resistance.
💡Temperature Effect
The temperature effect refers to the influence of temperature on the physical properties of materials, including their electrical resistance. In the video, the temperature effect is explored by subjecting the cable to different temperatures and measuring the resulting changes in resistance. It is shown that for most materials, including the copper in the cable, resistance decreases with a decrease in temperature and increases with an increase in temperature.
💡Ohms
Ohms is the unit of electrical resistance, named after the German physicist Georg Simon Ohm. In the video, the resistance of the cable is measured in ohms, with initial readings and changes documented in ohms. The ohms serve as a standard metric to quantify and compare the resistance of the conductor under various conditions.
💡Experiment
An experiment is a scientific procedure carried out to support, refute, or validate a hypothesis. In the video, several experiments are conducted to investigate the relationship between resistance and factors such as length, cross-sectional area, and temperature. The experiments are designed to demonstrate how these variables affect the resistance of the cable, providing empirical evidence for the principles being discussed.
💡Measurement
Measurement is the process of determining the quantity or extent of something using standard units. In the video, measurement is central to the experiments conducted, as it involves using a multifunction tester to accurately determine the resistance of the conductor in ohms. The measurements are essential for comparing the effects of different variables on the cable's resistance.
💡Direct Proportionality
Direct proportionality is a relationship between two quantities where an increase in one quantity results in a proportional increase in the other. In the video, direct proportionality is demonstrated by the relationship between the length of the conductor and its resistance, as well as the relationship between temperature and resistance for most materials. This means that if the length or temperature increases, the resistance also increases.
💡Inverse Proportionality
Inverse proportionality is a relationship between two quantities where an increase in one quantity results in a proportional decrease in the other. In the video, inverse proportionality is illustrated by the relationship between the cross-sectional area of the conductor and its resistance. It is shown that if the cross-sectional area is doubled, the resistance is effectively halved, indicating that these two quantities are inversely related.
Highlights

The experiment began with a 100-meter drum of 1mm² cable with a measured resistance of 1.78 ohms.

Doubling the length and cross-section area of the conductor also doubled its resistance.

The third factor affecting resistance is the ambient temperature surrounding the conductor.

A drum of cable was placed in the freezer overnight to observe the effect of temperature on resistance.

The resistance decreased to 1.66 ohms after being cooled, demonstrating that reducing temperature reduces resistance for most materials.

An experiment was conducted to confirm the values by repeating the process with the same 100-meter drum of cable.

Doubling the length of the conductor effectively rendered 200 meters of cable, resulting in a resistance of 3.17 ohms.

The experiment showed that doubling the length of the conductor doubled its resistance.

By shorting out both ends of the conductor, the length was effectively reduced back to 100 meters, and the cross-sectional area was doubled.

The resistance was halved to 0.77 ohms when the cross-sectional area was doubled, showing an inversely proportional relationship.

The experiment then explored the effect of increasing the conductor's temperature above room temperature.

A time-lapse video showed the resistance of the cable increasing as it got hotter.

The resistance increased significantly to 2.04 ohms when the cable was heated, demonstrating a direct proportionality between temperature and resistance.

Doubling the length of the heated cable to 200 meters resulted in a resistance of 4.08 ohms, confirming the direct proportionality between length and resistance.

When the heated cable's cross-sectional area was doubled, the resistance returned to 1.06 ohms, showing the inverse relationship between cross-sectional area and resistance.

The video concluded with the key takeaways: increasing length increases resistance, increasing cross-sectional area decreases resistance, and increasing temperature increases resistance for most materials.

The experiments provided a clear demonstration of the relationship between resistance and the variables of length, cross-sectional area, and temperature.

Transcripts

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