# Displacement Current and Copper Wire

• ovoleg
In summary, the conversation is about solving a question involving a copper wire with a current of 11 A and a resistivity of 2.1 × 10-8 ·m. The question asks for the uniform electric field, the rate of change of the electric field, the displacement current density, and the magnitude of the magnetic field at a certain distance from the wire. The conversation includes various attempts to solve the question and confusion regarding the formula to use. Ultimately, the formula is determined and the question is solved.
ovoleg
Hello guys. I gave this one the good ol effort and seem to have gotten stuck. Can anyone help?
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A copper wire with a circular cross-section area of 1.5 mm2 carries a current of 11 A. The resistivity of the material is 2.1 × 10-8 ·m. a) What is the uniform electric field in the material? b) If the current is changing at the rate of 4800 A/s, at what rate is the electric field in the material changing? c) What is the displacement current density in the material in part (b)? (Hint: Since K for copper is very close to 1, use =0.) d) If the current is changing as in part (b), what is the magnitude of the magnetic field 8.8 cm from the center of the wire? Note that both the conduction current and the displacement current should be included in the calculation of B. Is the contribution from the displacement current significant?

Okay I solved a) b) and c)

a) .154v/m
b)67.2v/M*s
c)5.94989E-10 A/m^2

now trying to get the last part

I got id=(jd)A

id=(5.94989E-10)*(1.5E-6)=8.92483E-16

And generalized version of Amepre's law states

Line integral of B*dl=mu-0(ic+id)

ic=(dE/dt)*(A)*(e-0)=8.92483E-16

So the Bc part is Bc=(ic/(2*pi*.088m)) = 2.0283E-21

And I got the same thing for Bd

Confused

Anyone? THANKS!

Please :) Need this last part to solve the rest

Last edited:
Nevermind I just got it, I did the Bd part correctly and Bc was to use 11A for the current.

Excuse me..anyone can teach how to solve this question? I need to know what is the formula to use when solve the question. Please help...

Last edited:

Hello, it seems like you have made some progress in solving this problem. For the last part, you are correct in using Ampere's law to calculate the magnetic field. However, remember that the displacement current and conduction current should be added together to get the total current in the wire. So the equation should be B = μ0(Ic + Id)/2πr, where Ic is the conduction current and Id is the displacement current. Also, the displacement current is usually much smaller than the conduction current, so its contribution to the magnetic field may be negligible. I hope this helps! Let me know if you have any other questions.

## 1. What is displacement current?

Displacement current is a concept in electromagnetism that describes the flow of electric charge that occurs in the space between two conductors, even in the absence of any physical movement of charges.

## 2. How is displacement current related to copper wire?

Displacement current is closely related to the behavior of electric currents in copper wire. As electric current flows through a copper wire, it creates a magnetic field which can induce a displacement current in nearby conductors.

## 3. What is the role of displacement current in electromagnetic waves?

Displacement current plays a crucial role in the generation and propagation of electromagnetic waves. It is responsible for the changing electric fields that create these waves, and is also a key component of Maxwell's equations which describe the behavior of electromagnetic waves.

## 4. How does displacement current differ from conduction current?

The main difference between displacement current and conduction current is that displacement current does not involve the physical movement of electric charges, while conduction current does. Displacement current is a result of changing electric fields, while conduction current is caused by the flow of electrons through a conductive material.

## 5. Can displacement current be measured?

While displacement current cannot be measured directly, its effects can be observed and measured through various experiments and calculations. It is an important concept in electromagnetism and plays a significant role in many practical applications, such as the design of electrical circuits and antennas.

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