How to Calculate the Resistance of Nichrome in a Series Circuit with Graphite?

In summary, the question asks for the resistance of the nichrome wire at a reference temperature, given that it is connected in series with a graphite wire and their combined resistance is independent of temperature. The temperature coefficients of resistance for graphite and nichrome are also given. The hint suggests using the resistances of the two wires at the reference temperature to write equations and solve for the resistance of the nichrome wire.
  • #1
Ugnius
54
10
Homework Statement
Two wires are connected in series. One made of coal , other one of nichrome. Series resistance is 5.8 ohms , what is the resistance of nichrome wire? Temperature coef. of resistance of coal -0.0005K^-1 , 0.0004K^-1 of nichrome
Relevant Equations
.
I don't really have any equations or idea how to solve this. I searched for relevant equations and only R=Rref(1+α(T-Tref)) pops up. I wasn't given any temperatures so I guess there must be some other way to solve this. Maybe anyone has idea how to approach this?
 
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  • #2
Also it's mentioned that this compounds resistance isn't affected by temperature. so maybe that would make difference
 
  • #3
Ugnius said:
Also it's mentioned that this compounds resistance isn't affected by temperature. so maybe that would make difference
Yes, that's critical. It let's you find the ratio of the two lengths. But there still doesn't seem to be quite enough info. Are you sure you have stated it completely?
(Coal?)

Edit: it let's you find the ratio of the resistances, not the ratio of the lengths, so it is enough information.
 
Last edited:
  • #4
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So this is the statement in my native language, i will translate it word by word.
E27. In order to get a conductor , with resistance independant from temperature , we combine coal and nichrome wires in series. If that stated combination has a resistance of 5.8 ohm , what is resistance of nichrome? αcoal=-0.0005K-1 , αnichrome=0.0004K-1. Thats it.
 
  • #5
Ugnius said:
View attachment 290949
So this is the statement in my native language, i will translate it word by word.
E27. In order to get a conductor , with resistance independant from temperature , we combine coal and nichrome wires in series. If that stated combination has a resistance of 5.8 ohm , what is resistance of nichrome? αcoal=-0.0005K-1 , αnichrome=0.0004K-1. Thats it.
Maybe the question is this:

A graphite wire and a nichrome wire are connected in series. Their total resistance is 5.8Ω and is independent of temperature.

For some reference temperature [probably 20ºC but it doesn’t matter] the temperature coefficients of resistance of graphite and nichrome are -0.0005K⁻¹ and 0.0004K⁻¹ respectively.

What is the resistance of the nichrome wire at the reference temperature?
_________

Hint: Call the resistances of the graphite and nichrome wires at the reference temperature ##R_G## and ##R_N##. Can you write down any equations, based on the information in the question, using ##R_G## and ##R_N##?
 

Related to How to Calculate the Resistance of Nichrome in a Series Circuit with Graphite?

1. What is wire resistance and why is it important in calculations?

Wire resistance is the measure of how much a wire resists the flow of electric current. It is important in calculations because it affects the amount of current that can flow through a wire and can impact the performance and safety of electrical circuits.

2. How is wire resistance calculated?

Wire resistance is calculated using Ohm's Law, which states that resistance (R) is equal to the voltage (V) divided by the current (I), or R = V/I. It can also be calculated using the formula R = ρL/A, where ρ is the resistivity of the material, L is the length of the wire, and A is the cross-sectional area of the wire.

3. What factors affect wire resistance?

The main factors that affect wire resistance are the material of the wire, its length, and its cross-sectional area. Different materials have different resistivities, longer wires have higher resistance, and thicker wires have lower resistance.

4. How does temperature affect wire resistance?

Temperature can affect wire resistance by changing the resistivity of the material. In most cases, as temperature increases, resistivity also increases, leading to higher wire resistance. However, some materials have a negative temperature coefficient, meaning their resistivity decreases as temperature increases.

5. How can wire resistance be reduced?

Wire resistance can be reduced by using a wire with a larger cross-sectional area, which allows for more current to flow through with less resistance. Additionally, using materials with lower resistivities can also reduce wire resistance. Keeping wire lengths short can also minimize resistance.

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