Current in wire - Please help

In summary: Happens to the best of us sometimes. Glad you got it figured out!In summary, the conversation is about calculating the current in a composite wire made of silver and copper sections, with a given potential difference and resistance values. The participants discuss finding the resistance of each section, using a voltage divider to determine the voltage across each section, and troubleshooting a calculation error.
  • #1
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Current in wire -- Please help

Homework Statement



A 1.63-m length of wire is made by welding the end of a 100-cm long silver wire to the end of a 63-cm long copper wire. Each piece of wire is 1.1 mm in diameter. A potential difference of 5.0 mV is maintained between the ends of the 1.63-m composite wire.
ρsilver = 1.47e-8Ωm
ρcopper = 1.72e-8Ωm


Homework Equations



What is the current in the silver section? (mA)
What is the current in the copper section? (mA)
What is the potential difference (voltage drop) between the ends of the silver section of wire? (mV)
What is the magnitude of the electric field in the silver? (N/C)

The Attempt at a Solution



Part A:
I assumed we had to find the resistance in each part, sum them, then find the current. The current from each section should be the same, correct? The value I have below (148 milliAmps) is wrong according to the online homework system.

Rs = ρL/A
= [(1.47e-8Ωm)(1.0m)]/[π(.0011m/2)^2]
= 0.015468Ω

Rc = ρL/A
= [(1.72e-8Ωm)(.63m)]/[π(.0011m/2)^2]
= 0.018098Ω

Rtotal = Rs + Rc = 0.033567Ω

V = IR
I = V/R
= (0.005V)/(0.033567Ω)
= 0.14895 Amp
= 148.954 milliAmps
 
Last edited:
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  • #2


Hello,
As long as you do not have any arithmetic errors in your calculations then you should be good. You have the right idea.
 
  • #3


sandy.bridge said:
Hello,
As long as you do not have any arithmetic errors in your calculations then you should be good. You have the right idea.

Cannot find any math errors. Been on this for 5 hours and can't move on until I get it. :/
 
  • #4


Okay, well the current will be the same in both instances as they are in series with one another. Since you know the resistance of each portion, you can apply a voltage divider to determine the voltage across each portion. For example,
[tex]V_{silver}=V_{total}\frac{R_{silver}}{R_{total}}[/tex]

I'm not entirely sure if there is something in specific you are having troubles with?
 
  • #5


Check your calculation for the resistance of the copper portion. I get 0.0114023 Ohms.
 
  • #6


sandy.bridge said:
Okay, well the current will be the same in both instances as they are in series with one another. Since you know the resistance of each portion, you can apply a voltage divider to determine the voltage across each portion. For example,
[tex]V_{silver}=V_{total}\frac{R_{silver}}{R_{total}}[/tex]

I'm not entirely sure if there is something in specific you are having troubles with?

FOUND IT, finally... somehow the value I got for Resistance through the copper is wrong.

Thanks for telling me I was on the right track so I knew it had to be a math error (or a programming error on their part).
 
  • #7


Hehe, no problem.
 

1. What is current in a wire?

Current in a wire refers to the flow of electric charge through a conductor. It is typically measured in amperes (A) and is essential for the operation of electrical circuits.

2. How is current in a wire generated?

Current in a wire is generated by the movement of electrons, which are negatively charged particles, through a conductive material. This movement is initiated by an external force, such as a battery or power source, which creates an electric field that causes the electrons to flow.

3. What factors affect the amount of current in a wire?

The amount of current in a wire is affected by several factors, including the voltage of the power source, the resistance of the wire, and the type of material the wire is made of. Additionally, the length and thickness of the wire can also impact the current flow.

4. How is current in a wire measured?

Current in a wire is typically measured using an ammeter, which is a device that measures the flow of electric charge in a circuit. The ammeter is connected in series with the wire, and the current can be read directly from the device.

5. What are some practical applications of current in a wire?

Current in a wire has many practical applications, including powering electronic devices, lighting homes and buildings, and facilitating communication through the use of electrical signals. It is also essential in various industries, such as manufacturing and transportation, for the operation of machinery and equipment.

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