Resistance of a cylindrical resistor

In summary, the conversation is discussing the use of formulas in solving a problem related to resistors. The participants suggest using physical thinking and understanding the concepts behind the formula instead of blindly applying it. They also mention the relationship between mass and volume in the context of the problem.
  • #1
Cici2017

Homework Statement


Screen Shot 2017-08-02 at 8.34.04 pm.png


Homework Equations

The Attempt at a Solution


Can someone tell me what formula to use? Is it p=RA/L? but what about the mass? Thanks~
 
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  • #2
What can you infer about the volume of the smaller resistors compared to the volume of the larger resistor?
 
  • #3
Dadface said:
What can you infer about the volume of the smaller resistors compared to the volume of the larger resistor?
p=m/V ,

if m half, V half,

V=πr2L

right?
 
  • #4
Cici2017 said:
Can someone tell me what formula to use? Is it p=RA/L? but what about the mass? Thanks~

I will tell you don't use any formula. It will do you no good, maybe less than none. Use physical thinking. Use a thought experiment like slicing a resistor in two.

Get the physical understanding then that will help you understand the formula!
 
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Likes Dadface and CWatters
  • #5
I agree with epenguin who has given you very good advice. If you do need to refer to a formula try to get a good understanding of what the formula is actually referring to. In many cases you will find it's common sense. Without understanding the formula you're just substituting numbers and probably learning very little.
 

1. What is the formula for calculating the resistance of a cylindrical resistor?

The formula for calculating the resistance of a cylindrical resistor is R = (ρ * L)/A, where R is the resistance in ohms, ρ is the resistivity of the material in ohm-meters, L is the length of the resistor in meters, and A is the cross-sectional area of the resistor in square meters.

2. How does the length and cross-sectional area of a cylindrical resistor affect its resistance?

The length and cross-sectional area of a cylindrical resistor have a direct relationship with its resistance. The longer the resistor, the higher the resistance, and the larger the cross-sectional area, the lower the resistance. This is because a longer resistor has more material for the current to flow through, increasing the resistance, while a larger cross-sectional area allows for more current to flow, decreasing the resistance.

3. How does the material of a cylindrical resistor affect its resistance?

The material of a cylindrical resistor plays a significant role in determining its resistance. Materials with high resistivity, such as ceramic or carbon, have higher resistance compared to materials with low resistivity, such as copper or silver. This is because the electrons in high resistivity materials have more difficulty moving, resulting in a higher resistance.

4. Can a cylindrical resistor have a negative resistance?

No, a cylindrical resistor cannot have a negative resistance. Resistance is a measure of how much a material impedes the flow of current, and it is always a positive value. Negative resistance would mean that the current increases as the voltage decreases, which goes against the basic principles of electricity.

5. How can the resistance of a cylindrical resistor be measured?

The resistance of a cylindrical resistor can be measured using a multimeter. The multimeter will measure the voltage and current across the resistor and use Ohm's law (V = IR) to calculate the resistance. Another way to measure resistance is by using an ohmmeter, which directly measures the resistance without the need for calculating it.

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