Calculate the resistance of iron if

In summary, the resistance of a rectangle bar of iron with a cross section of 2cm by 2cm can be calculated by using the equation R = (Pl)/A, where A is the area in meters squared and P is the resistivity of iron. It is not possible to find the resistance without knowing the length, but it may be possible to find the resistance per unit length by using the equation R/ℓ = ρ/A.
  • #1
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Homework Statement


A rectangle bar of iron is [tex]2cm[/tex] by [tex]2cm[/tex] in cross section. Calculate its resistance if the resistivity of iron is [tex]11 \times 10^{-8}\Omega{m}[/tex].

Homework Equations



[tex]R = \frac{Pl}{A}[/tex]

The Attempt at a Solution



[tex]R = \frac{Pl}{A}[/tex]

[tex]A = 2 \times 2 \times 10^-4 = 4 \times 10^{-4}m[/tex]
[tex]P = 11 \times 10^{-8}\Omega{m}[/tex]

How is it possible to find the resistance If I don't have the length?
 
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  • #2
looi76 said:

How is it possible to find the resistance If I don't have the length?

It isn't.

Maybe they are looking for the resistance per unit length:

[tex]\frac{R}{\ell}=\frac{\rho}{A}[/tex]
 
  • #3


To calculate the resistance, you need to know the length of the iron bar. Without this information, it is not possible to accurately calculate the resistance. I would suggest checking the given information again or asking for clarification from the person who assigned the homework. If the length is not provided, you may need to make an assumption or use an average length for iron bars in order to calculate the resistance.
 

1. What is the formula for calculating the resistance of iron?

The formula for calculating the resistance of iron is R = ρ * (L/A), where R is the resistance in ohms, ρ (rho) is the resistivity of iron, L is the length of the iron, and A is the cross-sectional area of the iron.

2. How do I determine the resistivity of iron?

The resistivity of iron can be determined by consulting a reference table or by conducting an experiment to measure the resistance of a known length and cross-sectional area of iron. The resistivity of iron varies depending on factors such as temperature and impurities.

3. What are the units for resistance of iron?

The units for resistance of iron are ohms (Ω). This is a unit of electrical resistance that represents the amount of opposition to the flow of electric current.

4. Can the resistance of iron change over time?

Yes, the resistance of iron can change over time due to factors such as temperature, corrosion, and mechanical stress. These changes can affect the resistivity of the iron, which in turn affects the overall resistance.

5. How does the resistance of iron compare to other materials?

The resistance of iron is higher than some materials, such as copper and silver, but lower than others, such as tungsten and nichrome. The resistivity of a material depends on its composition and physical properties, and can vary widely between different materials.

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