# How does Temperature affect Resistance?

• roxychc43
In summary, the conversation discusses the effect of temperature on resistance and the experiment that was designed to test this relationship. The experiment involved using a cylindrical bulb, a socket, connecting wires, a DC power supply, an ammeter, and a voltmeter to create a circuit and measure the voltage and current. The data was then used to plot a graph and determine the mathematical expression for the change in resistance as a function of temperature. The conversation also mentions the theoretical resistivity of the bulb filament, which can be compared to the experimental value to determine the material used for the filament. The conversation ends with a request for further explanation on the relationship between temperature and resistance, specifically in regards to the cross-sectional area of the bulb.
roxychc43

## Homework Statement

What is the effect of temperature on resistance? I was given an experiment to test this out... I was told to use a cylindrical bulb, a socket, connecting wires, DC power supply, ammeter, and a voltmeter. I was to connect the DC power supply to one end of the ammeter via connecting wires and the other end of the ammeter was to connect to the light bulb via connecting wires. The other end of the light bulb is supposed to be connected to the DC power supply via connecting wires... now that I have a complete circuit I was told to turn on the power supply and increase the voltage in .5 increments, taking corresponding measurements of current, but not to exceed 8 volts. I was then supposed to put my data in a table and plot a graph of voltage as a function of current.

And when I put the data into the graph it is a curve.. What would be the best fit equation for this curve? A power, exponential, Log?

I am also supposed to determine the mathematical expression that describes the change in resistance as a function of temperature. I am also supposed to find the theoretical expression that describes that relationship and then determine the experimental resistivity of the bulb filament. It tells me to look up what material is used for bulb filaments, and compare the theoretical resistivity to my measured value.

## Homework Equations

V=IR

I think the mathematical expression that describes the change in resistance as a function of temperature is

Rt=Rr(1 + alpha (deltaT))

and I know that Tungsten has a temperature coefficient of 5.6 x 10-8

## The Attempt at a Solution

-What seems to be happening to the resistance of the bulb as the current increases?
The resistance increases because according to the equation V=IR as the voltage increases the current increases.
-What do you think the reason is for this effect? Explain Clearly
I'm not to sure other than temperature? can you help explain why?

I don't know anything about the bulb other than it is a little cylindrical one and I don't know the cross-sectional area.

You might find this lecture useful at about 17 minutes or so. (Actually the whole thing is interesting, but in particular as to your heat /resistance question.)

Last edited by a moderator:

I can provide a response to the question of how temperature affects resistance. It is a well-known fact that temperature has a direct effect on the resistance of a material. This is because resistance is a measure of how difficult it is for electrical current to flow through a material.

As the temperature increases, the atoms in the material start to vibrate more vigorously, which creates more obstacles for the electrons to pass through. This increased resistance leads to a decrease in current flow, as described by Ohm's Law (V=IR). Therefore, an increase in temperature leads to an increase in resistance, resulting in a decrease in current flow.

In your experiment, as the voltage is increased in increments, the current also increases. This is because the voltage is the driving force that pushes the electrons through the circuit, and as the voltage increases, more electrons are able to flow through the circuit. However, as the current increases, so does the temperature of the bulb filament. This increase in temperature leads to an increase in resistance, which in turn results in a decrease in current flow. This explains why you observed a curve when you plotted voltage as a function of current.

The mathematical expression that describes the change in resistance as a function of temperature is known as the temperature coefficient of resistance, denoted by the symbol alpha (α). This coefficient varies for different materials and is typically given in terms of ohms per degree Celsius or ohms per Kelvin. The equation you provided, Rt=Rr(1 + alpha (deltaT)), is a valid expression for the change in resistance as a function of temperature.

In your experiment, you are using a bulb filament, which is typically made of tungsten. As you mentioned, tungsten has a temperature coefficient of 5.6 x 10-8 ohms per degree Celsius. This means that for every degree Celsius increase in temperature, the resistance of tungsten increases by 5.6 x 10-8 ohms.

To determine the theoretical expression that describes the relationship between resistance and temperature for tungsten, you can use the following equation:

Rt=Rr(1 + alpha (deltaT))

Where Rt is the resistance at a given temperature, Rr is the resistance at a reference temperature (usually room temperature), and deltaT is the change in temperature.

To determine the experimental resistivity of the bulb filament, you will need to use the equation:

ρ = RA/L

Where ρ is the resist

## 1. How does increasing temperature affect resistance?

As temperature increases, the resistance of a material also increases. This is because as the temperature rises, the atoms in the material vibrate more, causing more collisions between electrons and atoms. These collisions impede the flow of electrons, thus increasing resistance.

## 2. Why does temperature have an effect on resistance?

The effect of temperature on resistance is due to the change in the behavior of the atoms in a material as temperature changes. When temperature increases, the atoms vibrate more, causing more resistance to the flow of electrons.

## 3. What is the relationship between temperature and resistance?

The relationship between temperature and resistance is directly proportional. This means that as temperature increases, the resistance also increases. Similarly, as temperature decreases, the resistance decreases.

## 4. How does temperature affect the resistance of different materials?

The effect of temperature on resistance varies for different materials. For some materials, such as metals, resistance increases with temperature. However, for others like semiconductors, resistance decreases with temperature.

## 5. What is the scientific explanation for the effect of temperature on resistance?

The scientific explanation for the effect of temperature on resistance lies in the behavior of electrons and atoms. As temperature increases, electrons gain more energy and move faster. This causes more collisions between electrons and atoms, resulting in increased resistance.

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